Wood axle caps or hubcaps are generally used to 'cap' dowel rods, when the dowel rod is used as an axle. CAP14 FITS 1/4" DOWEL. CAP38 FITS 3/8" DOWEL. Cap14 has Outside Diameter 1/2. Cap38 has Outside Diameter 3/4. The holes in an axle cap only go part way through ( known as a blind hole).