Adjustable C-clamp style compressor will fit most heads including Hemi. Spring cup will fit stock springs up to 1.750" diameter and a "working window" to gain access to keepers that measures 1.100", which are too large for some small diameter spring/retainer combinations. Compressor has 9/16" hex for use with a wrench, ratchet or impact. This tool will handle spring pressures in excess of 1200 lbs. without slipping off.