Allstar 1-3/4 inch Maximum Spring Diameter 1200lb Rating C-Clamp Style Engine Valve Spring Compressor features engine valve spring compressors. It is a c-clamp style and is for use with a 1-3/4 inches maximum spring diameter. The compressor will fit most heads including the hemi. The spring cup will fit stock springs up to 1. 750 inches diameter and have a working window for access to keepers that measure 1. 100 inches. It is too large for some small diameter spring/retainer combinations. The compressor has 9/16 inches. There is a hex for use with a wrench, ratchet or impact. The tool will handle spring pressures in excess of 1200 pounds without slipping off. It is backed by a 90-day limited factory and is sold individually.