IMPORTANT NOTE: These gaskets are for standard GY6 150cc engine (most common). There are some GY6 125 & 150cc engine variations that use slightly different gaskets.
Check for these possible variations: (most of the variations are 150cc but there are exceptions).
1) If your cylinder has wavy fins (standard GY6 engines have straight fins).
2) If you have an ATV with a High/Low trans or w/ Reverse (the gear case and possibly the clutch cover gaskets are different). Some ATV engines have a different cylinder also.
3) If your valve cover is held on with 2 bolts (standard GY6 has 4 bolts). These engines use different head and base gaskets.