Review on Enhanced Performance with EC90 Carbon Fiber Bike Seat Post - 3K Seatpost for MTB Road & Mountain Bikes Cycling by Jake Hill

Cheap full carbon seat post that fits perfectly. Note that this seatpost is VERY FLEXIBLE when riding. In my case, it flexes back and forth on bumps in the road and noticeably flexes side-to-side under heavy seat forces. You can even see it flex as you drive. (I'm 6ft, 180lbs and a very calm driver.) Very strange feeling. The result is some dampening of road vibrations, but I have to wonder how much that flexing puts stress on the seat tube and carbon frame linkage bolt. It flexes so much that I removed it and won't be using it on my better bikes. I can't even imagine considering this for a gravel bike or MTB. Second, the manufacturing is a bit sloppy, especially around the seat clamp. See photo - the holes are not round and the mating surfaces are very rough. The post itself was well machined and accurate in diameter, fitting smoothly (with some carbon paste) into the seat tube. Metal bicycle frame. If you use it, I recommend regularly checking this very flexible seatpost for wear at all joints to avoid a possible catastrophic failure.