The 1/2" side on the 63710 is especially useful for removing the fuel supply line from the sending unit on 2001 and newer Chevrolet/GMC 3/4-ton and 1-ton trucks equipped with 6.6L Duramax engine.
The 3/8" side of the 63720 is especially useful for removing the fuel supply line from the center port of the sending unit on 2000 and newer Chevrolet/GMC Suburban and Tahoe/Yukon.
Also 1999 and newer Chevrolet Silverado pickups equipped with gas engines.