This 4-pack shim set is perfect for fine-tuning your door making shaper cutters. Some people like a tighter (or looser) fit when making cope and stick joinery. The shims in this 4-pc. set are .005" thick each and allow you to micro-adjust the tongue and groove on your door making shaper cutters. Use this shim set with any 3/4" bore shaper cutter. Also very useful for when you get your Rail & Stile shaper cutters back from the sharpener.