The ones I snagged from work last year don't have the center hole/plug but are just solid. Also, the seal isn't a foam disc, it's a ring of silicone.
You can jam a piece of tubing into that hole as long as it's a real tight fit. I'd remove the gasket material. I doubt it can be sanitized well.
Sightglass, Refractometer, Ball Valve, Weldless bulkhead, Thermometer, Decals, Stainless Steel Fittings, Compression Fittings, Camlock Quick Disconnects, Scale, RIMS tube, Plate Chiller, Chugger Pump, Super Clear Silicone Tubing, and more!New Stuff?