2" on mine also. Only place I've seen the 2.5" is the class V Hitch on my last Duramax. Perhaps all the 15k hitches have 2.5, any one know?
Jim and Jennie, Cats=Bittles and Potter, 2000 Dynasty 350 ISC
2013 Silverado 4x4 Towed with R1200GS in bed.
PROV23:4 Do not wear yourself out to get rich; have the wisdom to show restraint.