Differences between SFP-A and SFP-B
SFP-B TYPE: 14x12x17mm/ 0.55 x 0.47 x 0.67 in (LxWxH) Facing side is more like square.
SFP-A TYPE: 15x10x12mm/ 0.59 x 0.39 x 0.47 in (LxWxH) Facing side is rectangle.
SFP-B is a little big tight than SFP-A; SFP-A is suitable and flexible, SFP-B is durable and Tight. They are both fit in the slots of networking machines.