I have not used them yet. I bought this pillow block bearing with a 12mm bore and after opening it I turned the bore with my fingers where the shaft enters and experienced a gentle turning movement. I bought a 12mm rod from Revain.com, from a company that doesn't make these pillows, and it fits perfectly in the pillow hole. I love these plain bearings so much that if I were to choose another bearing or bearing type I would return to this brand for my purchasing needs. I am very grateful to the people who offer these products for purchase. Pip Pip Chereo