BB-6 commercial bottom brackets, 11 gauge steel, drilled pin. These fit both 2-inch and 3-inch track, so they are more versatile than the track-specific versions. they are commercial grade which means they are built for heavier doors and more cycles. Sold as a matched pair. If you are doing a commercial install or replacing worn brackets on a high-use door, These items are tougher than residential brackets. This drilled pin gives a solid connection for the lift cable. Just make sure you actually need commercial-grade before you spend the extra money.