4pcs Indoor Bike Trainer Stand Rocker Feet Adapters with 8pcs Tennis Balls, for Indoor Bicycle Trainer Training Stationary Bikes, Stability Accessories for Smart Bike Resistance Trainer

I researched rocker plates in the $300-500 category and came across this product, what a difference! I could barely tolerate 1 hour training sessions but not any more, terrific product!

Two issues with this product. A) It takes a LOT of force (like nylon faced hammer force) to get these parts to go onto my kickr core, and B) in the process of doing this, the tennis balls don't stay attached. The quality of the part design is meh. You can see that there's a fair amount of sink in the side face -- undoubtedly due to the differences in wall thickness. Ultimately, it functions. But, the install experience was not awesome.

I was a bit hesitant at first to get these thinking they were a gimmick. But, now after putting a couple hundred miles on the trainer with them on - I like them. Really like them. They went on just as directed, stay on fine, the balls stay put (hint - put the mounts on first, then insert the balls). The feel of the trainer with these on is like having a great set of tires on a smooth paved trail. I imagine after a year of regular use of the trainer the balls will lose their spring - but they're so easily replaced that won't be an issue.

These are amazing! They make the indoor trainer feel so much more plush when I'm putting down power, a lot more realistic of a ride-feel!Installation wasn't bad, I did need to use a rubber mallet to make sure they were securely fit, but I'd rather they be a little snug than loose. If you're moving the setup around - be prepared to pickup the tennis balls as they don't stay in the openings, but rather they sit in them.Overall I would happily recommend these to anyone who wants to upgrade their indoor trainer setup! :)

UPDATE: I ended up hearing back from the company. Their response was to say I should lubricate the rocker feet with hand sanitizer before hammering them onto the Kickr's feet. And that the visible injection molding defects are cosmetic and they apologize for any aesthetic concerns. While I appreciate the response, it doesn't give me any reason to change the review. Billions of products are injection molded daily and don't show the defects that these do, so they're either using substandard manufacturing processes or materials or they just don't care and are fine with shipping customers a product that isn't ready for market. You can make your own decision, but I'm not going to use lube and a hammer to install these because then there's no way I'm going to be able to get them back off if I don't want them on my Kickr.ORIGINAL REVIEW: Since we're in the middle of winter, I'm setting up my Wahoo Kickr Core for some indoor training. I don't love riding indoors on my trainer, but I thought that these rocker feet might make it a little bit better by giving the trainer the ability to move, or rock, a little so I wouldn't have that locked in kind of feeling. I've toyed with making a rocker plate, but I'm honestly just too lazy. These seemed like a low cost, low effort way of getting some of that real world movement back.Based on the product listing photos, I was expecting a set of 3d printed feet--and in fact, I had considered printing my own based on some designs that people have posted online. What arrived, however, are actually injection molded plastic pieces. They feel plenty sturdy, though the injection molding is clearly substandard, with lines/grooves in the molding where the plastic flowed into the injection mold but didn't completely coalesce. On top of that, there are these water marks and other kind of blemishes on the plastic like this was left out in the weather or something, so while it looks like it will function, it's just not an attractive product. Maybe this was a trial run and they'll sort out getting better injection moldings, but it feels like a prototype more than a polished product. The good news is that the tennis balls included don't feel like just regular tennis balls--they seem to be less pressurized, so maybe will give a bit more movement than a really hard tennis ball.The biggest problem with these rocker feet is that they don't fit my trainer. The inside diameter of the rocker foot that slips over the existing feet on the trainer is just a hair too small--no amount of pushing seemed to get it onto the trainer. So I tried taking the rubber foot off the trainer and inserting that into this rocker foot. Big mistake. The original Kickr rubber foot fits into the rocker foot (with a good bit of effort), but then the rubber foot won't fit back on the steel trainer foot tube. And now the rubber foot is pretty solidly stuck inside this rocker foot!I reached out to the company using the email address on the box to figure out what can be done about this and haven't heard anything back at this point. Based on the poor quality of the molding, inability to get this onto the trainer's feet to do what it is supposed to do as well as the lack of any responsive customer service, I would recommend a hard pass on this set. You can find alternative options at a similar price point that, based on other people's reviews, work better than these.