A Pressure Relief Valve upgrade or replacement for the Chronical line of fermenters from Ss BrewTech.,Features:,,,Standard replacement part for Half Barrel,,,Can be retrofitted to 7 Gal Chronical lid,,,Releases pressure between 2-2.5 psi,,,Food grade silicone O-ring,,,Use Dewalt DWA1783IR step bit for retrofit,,,For 7/32" inch hole diameter (in lid)