Have been looking for an answer to the product difference on these three for years, finally think I got it right. There is no difference, 2A, B, and C are simply different sized packages of the same product. Was working on a Tomos A35 clutch cover and needed to keep the paper gasket in place while reassembling. Product works very well. Don't use no. 1 as it hardens, no. 2 is non hardening. The popular silicon based sealants don't adhere to any oily surface.