That is a check valve to be able to stop the flow of O2, you need one of these:
Oxygen Regulator - Dual Gauge | MoreBeer
I got one off eBay for a lot cheaper, I would check there, for example:
HUDSON OXYGEN THERAPY REGULATOR NO 2100 - eBay (item 360187887484 end time Sep-16-09 08:22:45 PDT)
That way you can get a DO meter or know how much you are putting in.
On tap: #79 Berliner Weisse 1.030 9/20/12, Flanders, Barleywine, Wild Blonde (1.045 blonde hopped up and fermented with WLP644), #80B rett Saison
Fermenting: #82 Galaxy IPA, #83 Black IPA
Aging: #67 Bareleywine 1.116 11/07/2012, Flanders 2 batches 1.056 and 1.060 12/12/11 and 3/26/12, Kriek, 1.052 12/11,