"That is a massive difference."
HSA/FSA eligible via TrueMed
Free shipping in the US, EU & most of Canada
30 day money-back
Recommended by PTs and Chiropractors
Your back isn't the problem.
The chain pulling on it is.
Tight calves, hamstrings, and hips force your lower back to compensate. The patented foot hammock holds your foot at true dorsiflexion, the position that lets the whole chain release together. Five minutes a day.
- 99.5% of customers report a deeper stretch in their first session.
- Patent-protected geometry, refined with physical therapists. 150,000+ customers.
- A one-time tool for less than two PT sessions. HSA/FSA eligible. 30 day money-back.
Size
Standard fits 4'8" to 5'8". Large 5'9" to 6'2". X-Large 6'3" and up.
Color
Bundle & Save
Most Popular
1 Device
CastleFlexx Luxury, yours for life.
£184
Best Value
2 Devices
One for you, one for them. Save $80.
$478$398Save $80
Second device
Free shipping to the continental US, EU, and most of Canada.
30 days, full refund, no restocking fee. HSA/FSA eligible via TrueMed, so pre-tax dollars lower what this actually costs you.
Four Reasons Why CastleFlexx:
- Holds your toes at true dorsiflexion, the position a strap can't hold.
- Patent-protected design.
- Costs less than two PT sessions. Yours to use daily, for life.
- It helps treat chronic pain from back pain, plantar fasciitis, sciatica, hamstring tightness, and herniated discs.
Product Details
Materials and specs
CastleFlexx Luxury is built with brushed aluminum, premium cork handles, reinforced webbing, and a patented foot hammock for a secure, controlled stretch. The removable 2 lb FlexxBar adds assisted tension and converts the device into a full-body strengthening tool, so every session feels stable, premium, and purposeful.
Who CastleFlexx is built for
Built for people who are done guessing with straps, towels, and random stretches. Ideal for tight hamstrings, calves, hips, plantar fascia, desk-body tension, post-workout stiffness, post-injury mobility work, athletes, runners, 65+ users, and anyone who wants a repeatable way to move better at home.
Designed and shipped from the USA
Designed and shipped from the USA around a patented foot-hammock system, CastleFlexx gives you the leverage most stretches are missing. It supports better foot positioning, reduces hand strain, and helps you reach a deeper, more controlled stretch without forcing your body into awkward positions.
Shipping and returns
Free shipping for the continental USA, EU, and most of Canada on every device, plus a 30-day money-back guarantee so you can try CastleFlexx at home with confidence. Add CastleFit for guided follow-along classes tailored to your body, and cancel anytime in one click.
Real people. First stretch reactions.
Reaction-shoot first timers, post-surgery rehab buyers, athletes, and people who stand all day for work.
"It is very rare that I'm impressed by a piece of equipment."
"It helps me stretch areas I would not be able to do myself."
"Have you ever had a stretch this intense?"
"Great way to start the day. Really open up."
"You're gonna see me shocked at how well this thing's working."
"It's an ace in the hole if you drive a lot."
"It's crazy how much of your lower back pain actually comes from the stiffness in your legs."
"One thing that has minimized my injuries is this CastleFlexx."
If you are in the 1% that doesn't feel better in 30 days or less, just return it! 30 days, full refund, no restocking fee. That includes gifts.
Designed for the muscles behind the pain.
Ten minutes daily to target the tight muscle chains that often sit behind everyday aches, stiffness, and restricted movement. You control the depth at every step.
Back Pain
Back tightness often shows up when hips, hamstrings, and glutes get stiff or weak. Dan Castle went from level 10 pain in his lower back for two decades to being pain free after CastleFlexxing daily for 10 to 20 minutes, with MRI results to prove it. CastleFlexx helps you stretch the entire posterior chain using active and passive stretching so you can build strength and flexibility at the same time.
CastleFlexx is a stretching tool, not a medical device. Individual results vary. Consult your physician before beginning any new stretching or mobility program, especially after surgery or with an existing condition.
From the founder
Pain pills made me worse. Clinicians were helpful but too expensive every week.
This device fixed me.
Dan Castle herniated L4, L5, and S1. The medical menu read pills now, surgery later. He went looking for a third option and ran into a smaller problem first: he couldn't reliably hold the one stretch his clinicians kept assigning him at home. A strap slips, and the position is gone.
So he built a device that does the holding, then spent years refining the hammock geometry with physical therapists until it earned a patent.
"Your back is not the issue. Your back is the symptom of the issue."Dan Castle, founder
U.S. patent-protected geometry
Tight from the feet to the lower back.
That's the chain this stretch works.
Most chronic lower back tightness is downstream of tightness running up the entire posterior chain from the feet: calves, Achilles, hamstrings, and glutes. When the chain shortens, the spine takes more of the load. The patented foot hammock holds your foot at true dorsiflexion, the position that lengthens the whole chain together rather than one muscle at a time.
You control the depth with the strap. A yoga strap, doorframe stretch, or basic foot stretcher can't reliably lock the foot into this position. The foot rotates, the chain slackens, and the stretch ends up shallow.
★★★★★
"A stretch I didn't know I needed." After your first session, a regular hamstring stretch feels like a warm-up.Marcus T., first time user
Built for more than one stretch.
Eight named stretches that fit in five minutes.
Posterior chain
Posterior chain full stretch
Lower back
Lower back release
Hip flexors
Hip flexor decompression
Glutes
Glute and piriformis
Calves
Calf release
Achilles
Achilles and ankle
Feet
Plantar fascia and foot arch
Adductors
Inner thigh and adductor
Clinician reviewed
Designed alongside PTs. Used between appointments.
Physical therapists and chiropractors recommend CastleFlexx as a between appointment and post discharge tool. It doesn't replace your PT. It's the part of the home routine your clinician keeps reminding you to do, the one that's hard to hold with a strap and easy to skip.
Tap the video to hear a physical therapist and Dan walk through it.
★★★★★
"I purchased myself a cheaper strap first. Then I wanted to give this a try. The strap is ergonomic. But especially the quality of the handle, made of cork and metal, plus features like the added weight, makes it worth it."Antonio D., verified buyer
The pros stretch with it too.
Champions, Olympians, and household names keep one in the gym bag.
This thing is amazing.
"We don't use cheap straps anymore, we use CastleFlexx. I use it an hour a day. CastleFlexx is by far the best."
Ronald Acuña Jr
MLB All-Star, Atlanta
This thing is next level.
"This is the best stretching device on the market. I did a 10 minute review on my YouTube page covering everything someone passionate about getting out of pain needs to know."
Phil Heath
7x Mr. Olympia
Absolutely incredible.
"It is well designed and comes in beautiful colors too." (Instagram @marthastewart48, 2022)
Martha Stewart
Lifestyle icon
Stretch Like The Pros
Stop paying $100 a session. Own the stretch for $239.
You used to be able to do this.
★★★★★ 4.9/5 from 2,500+ verified buyers
★★★★★Jennifer S. Verified
This thing is amazing. It's improving my back pain and plantar fasciitis. I can't wait to see what happens after I've been using it for a while. It's so easy to use. I am very happy with my purchase.
★★★★★Leah H. Verified
I've had chronic back and leg pain for about 7 years and since using the CastleFlexx I've been able to wean off pain meds and can tell the difference when I don't use it daily. It only takes a few mins a day. Highly recommend.
★★★★★Salvatore A. Verified
Already impressed with the build quality. It feels sturdy and well-made. Given my goal of reducing low back pain and staying on the golf course longer, I'm optimistic this will be a worthwhile addition to my routine.
★★★★★Malina L. Verified
I have been going to PT for ankle and foot pain and realized this was cheaper than I spent on two sessions of PT, so I should give it a try. I already feel much better. I recently left it at home for a trip and missed it.
★★★★★Ben I. Verified
I have had chronic pain in my knees and IT band that have limited my ability to run and play sports. This thing really stretches me out like nothing else. Hoping extended use will allow me to get back into the sports I enjoy.
★★★★★Letwon C. Verified
I purchased the CastleFlexx after trying to stretch with several other straps after knee surgery. CastleFlexx increased the intensity of calf stretches and has aided in improving my range of motion. Much more comfortable than holding straps.
★★★★★Lucas D. Verified
Expensive item but worth it. Was able to use FSA money to pay for it so that helped a lot. I have never truly stretched like this before. 10/10 would recommend.
★★★★★Blake H. Verified
Picked it up for a gift and ended up getting another for myself. Solid sturdy build, comfortable cork grip. The product just works, and for my lower flexibility friend it lets him stretch by himself instead of asking for help.
★★★★★Perry R. Verified
It has been a game-changer when it comes to stretching. It grants you the ability for a deeper and more controlled stretch. I work in the sports industry and I could not recommend this enough.
★★★★★Michael M. Verified
I did a lot of power lifting previously and really needed to improve my flexibility. This has been a game changer and it's a device I actually want to use. It's always easy to travel with.
What you're actually paying for.
The price is $239. Fair question. Here is what it's made of and what it replaces.
One assisted stretch session
$100
"I just paid $100 to get stretched for an hour and I felt the same after the stretch." Verified buyer, hairdresser, 67.
Chiropractor, per visit
$75
"I'd been spending hundreds on chiro. Done with that now." Verified buyer.
Physical therapy, per session
$100+
Most clinicians ask you to come back more than once.
The $19 strap
$19
Holds nothing in position. The foot rotates and the stretch goes shallow. Cheap is its own cost.
CastleFlexx Luxury, once
$239
Patented hammock geometry, aluminum frame, cork and metal handle. Used daily, kept for life. HSA/FSA eligible via TrueMed, which lowers the felt cost further. 30 days to decide.
It's the same math as any good tool. Pay once, retire a recurring bill. 150,000+ customers did this math before you.
Frequently asked.
What size am I?
Standard fits 4'8" to 5'8". Large fits 5'9" to 6'2". X-Large fits 6'3" and up.
Is this safe for my age or my condition?
You control the depth at every step. The hammock holds the position, the strap sets the intensity, and nothing pulls further than you choose. Buyers range from college athletes to people in their 80s. If you're post surgery or working through a diagnosed condition, check with your physician first, then start shallow.
What's the difference between Luxury and Sport?
Luxury is the heavier home model with brushed-cotton fabric. Sport is the lighter travel model with quick-dry weave. Most first-time buyers pick Luxury.
Is it HSA/FSA eligible?
Yes. The device is HSA/FSA eligible via TrueMed at checkout. Pre-tax dollars cover the full eligible amount.
Does Medicare cover it?
Not directly. HSA/FSA covers the device and the program for eligible buyers via TrueMed.
Is this a medical device?
No. CastleFlexx is a patented stretching tool, not a medical device, and we don't make medical claims. It was designed alongside physical therapists and chiropractors, and many buyers come to it after surgery or while working through long-term mobility challenges, but it is not intended to diagnose, treat, cure, or prevent anything. Talk to your physician before starting any new stretching or mobility program.
What's the MRI in the founder's video about?
Dan shares his own imaging from before and after the years he spent building the device. It's the story of why CastleFlexx exists, told with his own records. It isn't a promise about your results, and CastleFlexx makes no medical claims.
Why does this cost what it costs?
Two answers. First, the patent: the foot hammock holds your foot at a position basic bands and towels can't, and the materials and assembly add up. Second, the math: one physical-therapy session is often $100 or more, and most clinicians ask you to come back multiple times. CastleFlexx is a one-time investment at less than the cost of two sessions, yours to use daily.
How many stretches can I do with it?
Eight named stretches in the basic library. The optional CastleFit app adds 200+ classes if you want guided programs.
What's the guarantee?
30 days, full refund, no restocking fee. If something goes wrong with the device after that, we'll repair or replace it. Built to last for life.
Where is it made?
Designed and assembled in the US. Manufacturing details available on request.
A patented tool. A one time cost. Yours to use daily.
$239, less than the cost of two physical therapy sessions, in a tool you keep for life. 30 day money-back if it doesn't feel deeper in your first session.
Recommended by physical therapists & chiropractors Patent-protected HSA/FSA Eligible 30 day money-back Built to last for life
Designed for stretching deeper. Not a medical device. CastleFlexx and CastleFit make no medical claims. The stretching device and program are not intended to diagnose, treat, cure, or prevent any disease or condition. Consult your physician before beginning any new stretching or mobility program, especially after surgery or with an existing condition.