The common uses for each size are:
30cm is used for:
1. Sidemount divers using 5th port or to some sidemount BCDs.
50cm is used for:
1. Some BCD inflator hose on BCDs with a short corrugated hose.
2. Sidemount divers using the "swing forward" hose routing.
70cm is used for:
1. Drysuit inflator hose on smaller individuals
2. Some BCDs that ave a longer corrugated hose length.
81cm is used for:
1. Drysuit inflation hose on most back-mount divers.
87cm is used for:
1. Drysuit inflation hose on larger framed divers.