Taking Measurements Measuring the Mounting Plate: To measure the top / mounting plate first measure the outside or the overall length and width of the plate. Then measure the bolt hole spacing, from the inside or outside of each bolt hole to the next, as pictured here... Measuring the Caster And Wheel: Mounting Height: Measure from the bottom of the wheel to top of the mounting point. Swivel Radius: Measure the center of the mounting point, (axis), to the outer most point of the wheel. Tread Width: Measure the overall width of the of the wheel. Wheel Diameter: Measure the overall height of the wheel from top to bottom. Measuring Stem Style Casters: Gauge: There are several style of stems. The easiest way to measure these is by using a “Hardware Gauge” (pictured below). You can buy one at any hardware or home store for about $2. Simply insert the stem into the drill bit holes and match it up to the size listed, ie: 7/16” (should be a snug fit). Wrench: You can also use a standard set of wrenches, for instance take a 7/16”. Use the open end of the wrench and put it on the stem, it should be a snug fit. Always measure the thickest area. Adjustable Wrench: Tighten the adjustable wrench around the widest part of the stem. Then take a ruler and measure the distance of the wrench opening.                                                                                                                                        This Gauge are not actual size... Measure Length: Use a ruler to measure                from the top of the stem to the base plate. Overall length of stem.