Exactly what these guys said- which is exactly what I wanted tbh so it’s great. Retention’s fine, actually pretty stiff- putting it back is pretty fiddly and it’s not the best bottle valve to drink from in a hurry either so all in all, I only try and fit it or take it when not moving.
If you’re a regular bottle user, they’re both pointless and not very good. But if you just want to occasionally carry some water they’re ace- quick local rides where you just want to wet your throat frisntance. I use mine for a light battery as well and perfect for that.
Doesn’t fit perfectly in one of my bikes, there’s no scope to move the “cage” as there normally would be, and the shock reservoir bumps it- so I reshaped the bottle to suit with hot air.
So all in all… Not a bottle cage replacement at all really but good if you wouldn’t usually want a bottle cage.
Oh- and the blurb doesn’t make this clear but you get 2 sets of bosses with each bottle, a coloured set and a black set (eh, at least I did- maybe the black bottles only come with one, who knows. But it’s a bonus that.