Kewlus DIY Cobra Bag Spring (KS2)

Kewlus DIY Cobra Bag Spring (KS2)

Regular price $39.95 USD
Regular price $49.95 USD Sale price $39.95 USD
Sale Sold out

Save a ton of money by making your own DIY Boxing Cobra Punching Bag with the KS2 Cobra Bag Spring. Increase the speed to your liking, yes with the KS2 the speed is adjustable! This spring is designed to fit easily onto a 3/4 inch pipe and simply held in place with a butterfly hose clamp. Increase the speed by moving the spring lower onto the pipe, thus reducing the number of active coils.


Check out the cobra bag kits that include this spring. Here's a video of the Top Section kit posted by a happy customer:

For DIY instructions on making your own base, check out

For complete DIY build instructions including a video using the Kewlus PRO Spring, go to

Cobra Punching Bag DIY

For more detailed and fully illustrated instructions get the Fighter DIY eBook (Third Edition. The Third Edition edition includes the Kewlus Spring Cobra Bag DIY plus 3 other awesome projects.

Review & Build by CSquared Boxing

Check out one of the top boxing gear reviewers on YouTube, Carlo Rosauro to see his hands on take on the spring as well as his full build 

Kewlus PRO Spring Review by CSquared Boxing

Shipping Info

Shipping is calculated at checkout with the following average shipping times.

USA & Canada

USA and Canadian orders will be shipped from Canada and takes just 2-3 days to most locations.

Limited Time Special Offer for USA customers: Orders to USA & Canada over $100 USD get free shipping.

Australia & NZ

Australian orders will be shipped from Queensland and takes just 2-3 days. NZ orders take 7-14 days.

The Rest of The World

All of the orders for the rest of the world are shipped from Canada and takes around 1 week to deliver.

Please note that you may need to pay import tax in some countries. Please check with your country's importation laws to find out how much tax would be charged.


You will receive an email with a tracking link as soon as your order is shipped from the warehouse. Please note that orders are not shipped on weekends or public holidays.

Pre-Ordering Products

Some products are available to pre-order and receive as soon as the are in stock. Please note that if you order these items together with other products, you whole order will not be shipped until every item in your order is available. All items in your order will be shipped together at the same time.

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Customer Reviews

Based on 8 reviews
Great product

I have been on the hunt for a budget cobra bag for a long time. I have a lot of leftover scrap from various other household projects around the house, too. With a little elbow grease, some basic tooling, some odds and ends I already had around, and a couple trips to the hardware store, I was able to build my own cobra bag at significantly lower cost and rescue some of my scraps from the landfill. I would highly recommend Kewlus products for anyone looking to up their training on a budget and any athlete who also enjoys a DIY project.

Justin S.
Really stellar product!!

I ordered just the spring, it shipped very fast, I think in a day or two. Works better than I expected and how you can adjust the speed with the DIY setup that Kewlus and Csquaredboxing cover in how to videos, you really cant beat it. And I'm not just talking about price. From the way it functions to how you can customize height, speed and base it truly is a hidden gem of the boxing world!

Erick S.
save yourself some money, HIGHLY recommend

The spring works amazing, and following your youtube tutorial made it super easy.
The homemade version is about 200 dollars cheaper then the cheapest cobra bag, and is better in every way due to how much adjustment you have. Like stated in your video, having everything be modular makes it so nice if I want to change out the bag, or if something breaks in the future. Highly recommend

KS2 Kewlus Spring

I have 2 of these. I fabricated my Own Cobra bag and it works perfectly. It cost me less than $100, which includes the Kewlus Spring and Noodle Foam and the wheels for my Cobra Bag. It's easy to move around. The rest of materials i used is from Scrap metal. Worth it to have one, specially if u know how to fabricate stuff. Easy job to make it.Thank's🤘🏼🤘🏼

Why do you want to spend almost 600$ for a tool that work the same?

The spring is deadly, you can fit it with cheap material, or with the kit, anyway anything you choose is okay, because this springs work the same like other cobra bag that you over paid, definitely the better choice. Thank you Reedy

Spring Only Purchase - Good

Overall, Spring reflex action is good but DIY build can be improved. Some of this could be be me but want to share issues I ran into during build.

1) Finding a 3/4 & 1 Inch metal pipe that fit between each other is tough. I tried HD, Lowes, Menards, etc and didn't have success. I spent 3-4 hours using hammer and sanding tools/brushes to make things bit more manageable.

2) Butterfly clamps are good but need something more sturdier. Jabs are great but if you plan to mix Jab with uppercuts you might send the pvc pipe flying upwards. I have to hold back power on uppercuts to overcome this issue. My thinking is that better or more clamps are required to overcome this issue.

3) I have no vibration or sound when I use the bag which is great. If you pay close attention to the build it should be mostly sturdy.

4) I did not build circular base and choose rectangular shape so I could put two 55 lbs plates (total 110 lbs) on the base. I attached flange to a rectangular shape pressure treated wooden board (approx 1.5 inch thick and 10 inch by 40 inch). I am realizing circular base would be better. I will rethink this later.

5) Note, with amount of time spent to get the metal pipes to fit in one another and $'s spent (Metal Pipes, pvc pipe, flange, pvc connector, butterfly clamps, bag, spring, duct tape, funnel, screws, and wooden board), I would highly recommend just buying the whole kit vs spring. Now, if you have some of these things at home already, then you may find it beneficial to buy spring and build. This was not the case for me.

Lastly, let me just point out that the bag is so much fun. I have gotten smacked in my face a few times but still enjoy very much. Thank you