These are specialized bearings that are used in many linear motion systems. The v-groove bearings generally ride on a rail or track. #10 Screws fit well with the inside diameter of this v-groove bearing.
The inside diameter is .1875 inches (4.7625 mm), overall outside diameter .7675 inches (19.54 mm), inside of the "v" diameter is ,.6425 inches (16.31 mm) and overall width is .3095 inches (7.86 mm). If a small v-groove bearing is desired, this is a good choice.