Protect your tools and your hands from damage. These are protective tool covers that fit over standard ER20 tool holders and add some extra safety when the tools are not in use. These are designed to be used with a flexible filament like TPU and have a snug fit over s standard ER20 collet nut. I've included 1" and 2" versions which indicate how much tool sickout each can accommodate. There are internal ribs that sit flush against face of the tool holder for added strength against impact.