1502 Series 4mm ID Spacer (6mm OD, 19mm Length) - 4 Pack

This spacer is the epitome of the classical maker’s Keep-It-Simple philosophy! Is it this spacer’s 4mm ID that's caught your attention, as you can use it as a spacer 4mm shaft? Or is it its 6mm OD—which you can utilize it to affix it to a clamp, or make use of for running a 6mm ID bearing? 

19mm length spacers in particular allow you to box 1121 Series Low-Side U-Channel together given the inside dimension of each piece of channel is 9.5mm. Boxing channel with these spacers creates a very stout framework while minimizing real estate. And when it comes to general utility, spacers of various lengths are nice to have on-hand when exploring the depths of your innovation.