Overview Reviews Product Description Designed with a single-flute cutting edge for great control, the Unibit® #21 13/16" - 1-3/8"Step-drill bit makes true round holes every time.It can power through a variety of surfaces, including: stainless steel, copper, brass, aluminum, plastic, and laminates.The 3-flatted shank prevents bit from slipping in drill chuck. Irwin Tools Catalog Product Videos Custom Field Manufacturing country US Product Reviews Write a Review Write a Review × Irwin UNIBIT® 13/16 - 1-3/8" #21 High Speed Steel Step Drill Bit 10221 Rating * Select Rating 1 star (worst) 2 stars 3 stars (average) 4 stars 5 stars (best) Name Review Subject * Comments *