Nikon AR-4 Double Cable Release for Nikon FE, FM, F2 Series Cameras (#2636). To enable automatic diaphragm operation with the PB-4 or PB-5 Bellows, use either the BR-4 ring, or the BR-2a ring plus BR-6a ring. With the optional Nikon release adapter AR-8, the AR-4 Double Cable Release can be used with F3 series, FA, FE2, FM2, and FG Cameras.