The different types are:

• Tripod Mount Ring A (W) or A II (W) [hinge] for 70-200mm f/4 L (for both IS & non-IS versions), 300mm f/4 L, 400mm f/5.6 L,
• Tripod Mount Ring A (B) or A II (B)[hinge] for 200mm f/2.8 L, 200mm f/2.8 L II, 80-200mm 2.8 L
• Tripod Mount Ring B (W) [no hinge] for 70-200mm f/2.8 L (IS, non-IS, IS II), 100-400mm f4.5-5.6 L, 300mm f/4 L IS
• Tripod Mount Ring B (B) [no hinge*] for 100mm f/2.8 Macro, 180mm f/3.5 L Macro & MP-E 65mm f/2.8 Macro
• Tripod Mount Ring C (W) [hinge] for for 70-300mm f/4.5-5.6 L IS, 28-300mm f/3.5-5.6 L IS
• Tripod Mount Ring D [hinge] for 100mm F2.8 L IS Macro Lens

The interior ring dimension for each are (note well they do not go "in order"):

• Tripod Mount Ring A 65-66mm
• Tripod Mount Ring B 78mm
• Tripod Mount Ring C 82mm
• Tripod Mount Ring D 68-72mm

Most have (B) and (W) markings on them, meaning Black and White respectively. A and A II are interchangeable.

Most Canon rings have a hinge that allows the collar to be removed without dismounting the lens. Only Canon "B" rings do not have a hinge and do require the lens to be dismounted to remove the ring. 3rd party rings come in both hinged and hinge-less designs. Some users prefer the hinge-less version for ease of use when using the lens collar to transition from landscape to portrait orientation. Other users prefer the ability provided by the hinge to add/remove the collar without dismounting the lens.

Lenses that use the Tripod Mount Ring B (W) have lugs that fit inside a grove in the lens collar. The collar also has slots to allow clearance for the lugs when the collar is removed.

*The Tripod Mount Ring B (B) pictured at Canon's online store appears to have a hinge. This is in fact an incorrect picture of a 3rd party Tripod Mount Ring. (you can read "for Canon" on the mount) The Tripod Mount Ring B (B) pictured at B&H is clearly marked correctly and is not hinged and does include the slots and groove for the lugs on the lenses that include the Tripod Mount Ring B (W) as standard equipment. The only lens that uses the Tripod Mount Ring B (B) not supplied with the collar as standard equipment is the EF 100mm f/2.8 Macro (non-L) which does not have lugs that fit in the slots and groove. There is a plastic adapter included with the B(B) ring that fits the EF100mm 2.8 USM Macro lens for use with the B(B) ring.