Use of corner connectors enable track to be assembled into a rigid frame that can attach directly to the surround of a condenser coil opening. The track creates an additional .75″ stand-off away from the outer surface of the unit – thus helping to enhance coil protection. For internal filter applications, the rigid frame can accommodate different filter grades and be slid into an internal filter rack as a pre-filter which will protect pleated and box style filters as a Pre-filter.