Groz Push On Button Head Coupler Button Head Fitting Size: 5/8″ or 16mm (PCN/3/N) and 7/8″ or 22mm (PCN/2/N) Thread Size: 1/8″ NPT A range of couplers for use with button head grease fittings, found mostly on heavy machinery, agricultural or contractor’s equipment Zinc die cast construction Couplers conveniently slide over the face of the button head fitting All couplers have a metal seal that imparts increased resistance to wear