MTB Cassettes- are they universal to wheels Are cassettes all standard as fare as fit on the wheel?  For example, can I can swap out a new Shimano for my old SRAM without looking at specifications for fit?
There are currently 4 MTB freehub/cassette standards for SRAM/Shimano drive trains:


7 speed - Shimano/SRAM - based on Shimano HG
8/9/10 speed - Shimano/SRAM (a 7 speed cassette with a 4.5mm spacer also fits) based on Shimano HG
Shimano 11 speed - fits an 8/9/10 freehub (MTB only) - based on Shimano HG
SRAM 11 speed - XD driver freehub - SRAM proprietary system


Campagnolo has two spline patterns also, 8 speed and 9/10 speed.

Unless you a running a SRAM 1x drivetrain it's generally safe to say cassettes will be compatible for the same number of gears.