The 100762825 Rotatable Bolt Ring is designed to join NW250 size ISO-MF vacuum flanges to NW250 size ISO-BF bolted flanges. Aluminum rotatable bolt rings have the same outer diameter and bolt pattern of the matching size ISO-BF flange allowing ISO-MF and ISO-BF flanges to be bolted together using a bolt and nut set. A 304 stainless steel retaining ring is included to retain the bolt ring. Series 76 ISO-BF flanges and seals are designed to be tightened to metal to metal contact. It is important that the bolts not be over tightened or warping of the flanges could result. The torque rating for flange bolts is 7 to 10 pounds per foot.