66784 Stud Mount Valve Spring Compressor For all 3/8' & 7/16' Rocker Studs COMPATIBILITY: For all 3/8' & 7/16' Rocker Studs. Specially designed for compressing valve springs with the cylinder head on block. FUNCTION: Easily and quickly remove valve spring from an assembled engine for checking or replacing. 360 DEGREES ROTATION DESIGN: Handle swivels 360 degrees to compress and lock spring down to desired height and remove handle while removing or installing keepers. Press down to compress coil spring, then remove valve keepers. Release slowly. PREMIUM MATERIAL: Crafted from heavy-duty steel for professional level reliability and durability, a zinc plating for added corrosion protection, providing a long-term service. Rubber grip handle for anti-slip and labor-saving. Part Number66784 Package Include1x Stud installation valve spring compressor removal tool