What tool to remove rear differential filler plug on a 01 s-10 blazer?

The rear differential filler plug on a 2001 S-10 Blazer typically uses a 10mm Allen wrench (also called a hex key). However, it's *always* best to double-check with a repair manual specific to your vehicle's year and engine to be absolutely sure. Sometimes, depending on wear and tear, a slightly oversized wrench might be needed. Make sure the wrench fits snugly before applying any significant force to avoid stripping the bolt head.