If I were seriously wanting pepper spray for a bear deterrent, I would not be using a small reservoir 4.2 oz something designed for human muggers or rapists. (I would rather have that second hand on the handgun in that situation.) You should consider carrying a large canister of real bear pepper spray like a 9.2 oz UDAP product or 10.2 oz Counter assault. They are both designed for bear situations. Check out the specs and go with something effective, and with the capacity to really blast a dose out there. Even those big canisters empty out fast!
