Bottle Cap Feeding Systems specification should start with the real closure.
A bottle cap feeding system is the complete route from bulk cap storage to cap handover. It can include a hopper, cap elevator, vibratory bowl, sorting device, chute, escapement and level control. The correct route depends on closure shape, speed, capper type and changeover expectations.
For a better buying decision, the useful comparison is not only hopper size or headline speed. It is how the feeder behaves with your closure, how the capper receives the cap and how easy the line is to run after changeover.
The safest specification route is to start with real closures, target output, line photos and the exact point where the cap must be presented. That avoids choosing a feeder on a generic speed figure that does not match the cap or capper.