Another factoid on orientation of the bulb. I use a fuel hose with a bulb to siphon diesel fuel from 5 gallon jugs into my tank. I get the siphon started by using the squeeze bulb. The other day I was doing this and I couldn't get the siphon started with the bulb oriented facing down or horizontally. I then placed it so it was vertical at the mouth of the jug with the arrow pointing up and with two pumps it pumped fuel and started the siphon, so there is definitely an advantage to the orientation. This is not to discredit other posts here about air leaks and such, but this experiment really showed a difference in performance of the bulb.