Protected 18650s and unprotected 18650s may have a difference of 3-4mm in length.
Protected 21700 and unprotected 21700 may have a difference of 5mm in length.
Most flashlights that accept 18650 will accept both protected and unprotected 18650s, but not all (eg. Emisar D4, Astrolux S42, etc. do NOT fit protected 18650s).
Protected 21700 are still very rare, I doubt flashlights that are not designed with those in mind will fit them, because the springs have to accommodate 5mm length (there will be a lot of current drop, for flashlights that use high-drain cells, having the extra length will mean a big current drop due to the size, as per my understanding)
Does anyone know the reason 18650/21700 was chosen over 26650 for the L21A ?? looking at the range of good capacity 26650 cells available i would of thought that was a better option?
Does the L21A have a different reflector than the L2? thinking i should just buy the XHP35 Hi emitter, driver and an L2 host and save a lot of aggro trying to get 21700’s ?
Yes 1 cell only (should of mentioned that) I have been searching for a 2s 2.3amp boost driver but as yet not found anything sadly… Trouble is being in the UK 21700 is hard to come by and id need a different charger as well , think il go with the L2 that way at least if i ever find a suitable 2s driver i can add a second battery
Im guessing there is no 6v XHP35 hi emitter available?