JBL Professional Assembly Backcan for JBL CSS8008 or CSS8018 Speakers, 8-Inch, Pack of 6

Additional Information?Bolt Mount Circle: 4 points on 11.25" diameter?Air Space: 4 liters?Conduit Knockouts: 4 on sides spaced at 90? and 1 at center of top panel?Attachment Points: 4 points on 11.25" diameter with clip nuts for 4 screwsSafety Approvals:?UL1480?UL2043?NFPA 90?NFPA 70?S7232/UL?cUL?IEC60849/EN60849