Major accessories for the F2 included the Nikon MD-1 (introduced in 1971) and MD-2 (1973) motor drives, providing automatic film advance up to 5 frames per second, 6 if the mirror was locked up, plus power rewind. They both required a Nikon MB-1 battery pack holding 10 AA or LR6 batteries in two Nikon MS-1 battery clips. Note that the 5 frame/s rate required that the F2 have its mirror locked up and the MD-1 or -2 be loaded with two Nikon MN-1 nickel-cadmium rechargeable batteries. (These batteries are long since dead.) With the mirror operating, the maximum advance rate is 4.3 frame/s; with AAs, the rate is 4 frame/s. The addition of the MD-1 or MD-2 greatly increased the overall weight of the camera. With a fully loaded MD-2/MB-1 and 50mm lens, the F2 would weigh in at just over six pounds.