Irwin 1/4" x 18" Installer Drill Bits 39104 This product is easy to use. This product is highly durable This product is manufactured in China 18" long, 1/4" diameter, .230" shank Hole in flute (head) makes it easy to pull wires through hole in wall Boring action is faster, smoother, cleaner in most every material encountered in wiring installations Longer flute section for deeper boring Special flute finishing process assures quick chip removal, no clogging, no binding