A must on any hovercraft, yet a common trouble maker, we're picky about the quality of our primer bulbs.  After testing and rejecting numerous different manufacturer's primer bulbs, we finally found one that stood out.  This is a nice, heavy duty fuel primer bulb with good back flow prevention and sturdy nipples for 1/4" or 5/16" hose attachment.  They do cost more than the generic bulbs, but the quality level and life span more than makes up for it.