Review on 🚲 Upgrade Your Bike's Seatpost: NIUAWASA Aluminum Alloy Seatpost Adapter Shim for MTB, Mountain, City, and Road Bikes - 25.4/27.2/28.6/30.4/30.8/31.6/33.9/34.9mm Sizes by Owen Houser

I needed a seatpost spacer to go from 31.6 to 33.9. (My current seatpost is 33.9mm). I got this spacer for a longer seat post with 31.6mm and 350mm suspension (31.6 to 33.9). I also got a different brand spacer for an even longer seat post (27.2mm x 400mm) so the spacer is between 27.2mm and 33.9mm. This gasket is clearly aluminum. It's thick, doesn't flex at all, and is longer. Compared to this gasket, this brand really looks and sounds like plastic. I am not at all satisfied with this purchase. (Also, the seatpost keeps slipping. It never slipped with the 33.9mm seatpost that came with the bike. I'll have to wait and see if the 400mm seatpost slips with a different brand of padding.) I just did applied some gel. This is to prevent the carbon fiber seat posts from slipping. That's rough. Just take a look. But even if it works, I shouldn't use it.