You can join an ISO-BF bolted flange to an ISO-MF an ISO-MF Multi-fastener flange by using a rotatable bolt ring on the ISO-MF flange. In attaching a rotatable bolt ring to an MF flange, the ring is first passed over the flange with the larger bore of the ring facing outward from the open port. The split retaining ring is then snapped into the groove on the periphery of the ISO-MF flange. Then the bolt ring is pulled forward into position. The vacuum flanges are then joined using nuts and bolts.