Mesa LW Floating Plunger

Modest upgrade to the original plunger head. Uses an optimized head profile to allow for less vacuum when pumping back, and greater seal when going forward, in addition to saving 1g from the original. Performance is unchanged, but it's now slightly easier to assemble and prime.

Note: This does not use the same O-ring as the original! This uses a thinner -131 size O-ring.