with my recent RF 30 purchase I also got some tooling...including many R8 Collets. However this one was an odd ball. I first thought it was an R8 ER collet holder but the size of the collet does not seem to match the known dimensions of ER collets as found here....https://littlemachineshop.com/info/er_collet_sizes.php.... too long for an ER 40 but too narrow for an ER 25