Drop a small, 1/2" rubber grommet into the collet before inserting any of our bits in our matched sets.

After considerable research and more than 10 years' experience using this method, we have determined that the shanks of all our matched-length Sommerfeld bits will bottom-out identically in the collet...and allow the collet to be drawn down into its sleeve the same precise distance...every time...without multiple router height adjustments.

That's why we include one of these grommets with every matched Sommerfeld Router Bit Sets.