Check the listing for details. Precision Spiral Mortising Chisel Set Square Hole Drill Bit 1/4" 5/16" 3/8" 1/2". Color: Black, Condition: New. Listed at 21.14 USD. Product Description Package includes: 1 X 6.4mm (1/4") Twist Drill, 1 X 8mm (5/16") Twist Drill, 1 X 9.5mm (3/8") Twist Drill, 1 X 12.7mm (1/2") Twist Drill Square Hole Drill Bits Mortising Chisel Set (All of Sizes) Come with 4 different size for your choise. Square hole, 1/4"(6.4mm), 5/16"(8mm), 3/8"(9.5mm), 1/2"(12.7mm). Corresponding shank, 7/40"(4.4mm), 2/9"(5.8mm), 17/64"(6.9mm), 3/8"(9.5mm). 4PCS High Speed Steel Woodworking Square Hole Mortise Drill Bit Set Chisel Drill Bits, mortising attachment for drill press, fits all mortising machines and drill press attachments. Square hole drill is mainly used for woodworking aspects. The square hole drill bit is composed of a center drill core bit and a sharp outer drill sleeve. Made of high-speed steel. Heat treatment. HRC48 - 50. Offers high hardness, lengthened core, and high concentricity, - Fits all mortising machines and drill press attachments. Square hole drill is mainly used for woodworking aspects, Durable, exquisite workmanship, for efficient performance and long life. 4 pieces a pack with different slot diameter to meet your needs - Professional drill bit, suitable for construction, installation, renovation, decoration industry, etc. Woodworking drill bit sets with long drill core and square chisel, easy to lock the hole on the wood, then you can get different mortisers quickly. Also, it is labor saving. Reduce labor intensity of construction workers, speed up the construction speed, reduce construction costs for construction, installation, renovation, decoration industries.