This professional tap and die set is engineered from ultra-tough tungsten molybdenum steel to retain precise cutting edges after use. Vacuum hardened for clean and durable threads Tapered starts for easy alignments and straight cutting Precision ground tap and die threads provide smooth and easy cutting Self centering die wrench provides more accurate thread cutting Double-end adjustable tap wrench for large tapping work T-handle, collet style tap wrenches for normal tapping applications Thread gauge provides quick and easy thread pitch identification Premium heavy duty storage case included.