We have a few choices when it comes to choosing a piston pin. 5115 Material pins are chromium alloy and steel case hardened to 58-64 Rockwell C designed for normal wear and tear. 52100 Material Pins are high carbon chromium-bearing steel made of aircraft quality alloy and case hardened to 54-56 Rockwell C for high load capacity. 9310 Material Pins are high quality low carbon and are case hardened to 59-63 Rockwell C for turbo or nitrous applications. *5115 Material Pin* * Standard grade chromium alloy steel * Case hardened to 58-64 Rockwell C * Ground to a surface finish of .15 Ra or better * Designed to withstand the normal wear and tear of an aftermarket engine *52100 Material Pin* * High carbon, chromium-bearing steel * Aircraft quality alloy * Case hardened to 54-56 Rockwell C * Through hardened * Ground to a fine finish * Designed for high load capacity * Designed for outstanding wear and abrasion resistance *9310 Material Pin* * High quality, low carbon, case hardened steel * Case hardened to 59-63 Rockwell C * Ground to a superfinish (.025 Ra or better) * Designed for use in applications which require high surface strength combined with high core toughness * Excellent to use in applications where high contact stress is combined with high shock and impact loading, such as turbo / nitrous applications