This is the same basic model as the SL-515 except it mounts into a wall using "Jacks". These jacks are designed to stay in the wall but with the idea that the fixture can be removed during packaging and transit. This also allows the clean look of no mounting brackets. The arms hinged and telescoping to allow maximum adjustment. Jacks are mounted 1.125" on center in .406" diameter holes. It is compatible with Banana-Jack connection style transformers and extensions.