This is very simple. All you have to do is look at your tyre size. The tyre size will be marked on the tyre sidewall. 26"MOUNTAIN BIKE ! Standard hub spacing of 135mm on the rear wheel and 100mm spacing on the front wheel.
26" Mountain Bike Rear Wheel Bolted Screw On with SEALED BEARINGS
8 SPEED 26" MOUNTAIN BIKE REAR WHEEL disc and rim brake including 8 freewheel
Mucky Nutz Mountain Bike Rear Mudguard - 26-29" - Black
26" MOUNTAIN BIKE WHEELS, DOUBLE WALL, 6, 7, 8 SPEED, FRONT, REAR, BOTH
26" MOUNTAIN BIKE 6 SPEED REAR WHEEL, 6 SPEED FW FITTED, DISC AND RIM BRAKE
26" MOUNTAIN BIKE 8 SPEED REAR WHEEL, 8 SPEED FW FITTED, DISC AND RIM BRAKE