Print both the base and cap portions of the bearing. Once printed check and clean out any excess material in the inside and outside gaps in the base profile and under the small clips on the cap profile. Dry fit the pieces to ensure the clips fit through the gaps in the base and there is enough space for the two parts to surn freely. Take the two parts apart and place the 40-6mm ball bearings in the track, lubricate as required, and place the cap back on the bearing. Can be glued to a base plate and a top plate as needed.