Bi-Metal Reciprocating Saw Blades are suitable for thin sheet metal, man-made board, woods with nails, all wood and plastic. The bi-metal blade is the combination of both a high carbon steel (HCS) body and a high speed steel (HSS) cutting edge. Giving strength and flexibility at both low and high temperatures. A tough shatter resistant blade that keeps its edge longer. Extended service life leads to greater cost effectiveness per blade.