Mini V-Wheel Spacers are intended to be used with the Actobotics Mini V-Wheels. The spacers have an OD of 5mm so that the bearing of the Mini V-Wheel slides over; the length is the same as the overall width of the Mini V-Wheel. The spacer acts as a collar to keep pressure from being applied to the bearings within the Mini V-Wheels when a fastener is tightened down to hold the assembly together. These spacers can be used in conjunction with our 6-32 standoffs if you want to create an overall height other than what we offer in the Mini V-Wheel Standoffs. They can be paired with a single 0.250" OD spacer so that a long screw can pass through both spacers and into a threaded hole or they can be used in-between multiple 0.250" OD spacers to create a 'Mini V-Wheel Sandwich'. Check out the 'Build Ideas' images for some other great usage illustrations. These spacers are sold in packs of 4.