The BT8BS is a two piece set which includes the BT8B Bolt Lock and the BT8 Gooseneck Coupler Lock.  The BT8B Gooseneck Bolt Lock provides a secure way to lock the coupler tube to your trailer.  Preventing someone from removing the tube with your coupler lock on it and replacing the tube with one of their own.  The BT8B also provides a storage bracket to hold and lock the BT8 Gooseneck Coupler Lock.  With this feature you will always have your Gooseneck Lock with the trailer and not left behind or in another vehicle.  This lock works with 5/8" & 3/4" bolts at spacing from 2 1/2"- 5" between bolts.