Originally Posted by
JiveTurkey
It might be Shimano-compatible. What kind of shifter and rear derailleur is on it? If it's Shimano or lower-level SRAM, then any Shimano/SRAM-compatible cassette with the same number of cogs will work. There are a few caveats though.
The derailleur is a Shimano Tourney, but the shifters are off brand (Gripshift, I think). One more thing, I just noticed the freehub has three tiers. Is that normal on mountain bikes? I'm pretty sure my road bike freehub only has one level.