Safe-T-Seal, Professional Drain Line Test Plug, Features Never Over Inflate, Patented Pressure Relief Valve Releases Excess Air While Still Holding Pressure, Waffle Pattern Exterior, 3' Heavy Duty Pull Strap Keeps User Safely Away From Danger Zone, Heavy Duty Handle With Built In 3/4" Hex Wrench To Remove Air Valve For Water Fill Application, Inflates Using Water Or Air, Best Inflation Pressure Is 50 PSI Maximum Back Pressure Of Water Is 30', If Water is Used, Unit Will Both Test & Fill Drain Simultaneously, Fits Drains 3" To 4" Diameter.