Add these rotational inserts to any 500 Series Bearing Block. These R-8 bearing inserts have a 1/2 inch diameter bore. These are great for heavy duty applications where smoothness is a must. One R-8 bearing per insert.
To use, remove the needle bearing that come with the 500 Series Bearing Block and replace with this insert.
500 Series Bearing Block sold separately here: https://store.berkeysystem.com/500-series-bearing-block/