Our bearings are lead indium over bronze steel base. The common mane for these bearings beings tri-metal. We tyr and stock the following sizes. Std., .010, .020, and .030. If you need larger, give us a call and see what we can do for you. These are a whole lot stronger than the standard lead over steel bearings. Standard bearings are ok for very light touring, but why put an engine together with weaker bearings?