What is the lug size on a 1991 GMC sierra?

The lug size for a 1991 GMC Sierra typically features a 6-lug configuration with a lug bolt pattern of 6x5.5 inches (or 6x139.7 mm). The lug nut size is usually 7/16"-20. However, it's always best to verify the specific vehicle's specifications, as variations may exist based on the model and trim.