The Op/Tech USA System Connectors: Sling Strap Adapter (Black) is designed to convert most Op/Tech straps into an over-the-shoulder sling. The adapter clips onto an optional strap pad. There are 2 Uni-Loop connectors included that allow for use with a pro battery pack and other options for carrying gear. When using the adapter the camera or binoculars will glide freely up and down on the sling strap.