Square gauge blocks are a quick way to make many easy, accurate set-ups. A great way to make exact depth movements on plunge routers. On table routers, they're perfect for setting distances from the fence to the cutter, or for checking the bit height above the table. Supplied in 1/8", 3/16", 1/4", 3/8", and 1/2" squares. Blocks can be "stacked" to cover a wider range of sizes. A very helpful tool! 5 piece set - 4" long.