Shop router bits by shank size when you already know the collet your router or CNC machine accepts. Choose 1/4 in, 1/2 in, 6 mm, 8 mm or 12 mm shanks to match your tool exactly. For most projects, start by selecting the router bit profile you need, then use shank size to narrow the results. A correct shank-to-collet fit helps improve safety, stability and cut quality.