1/2" Drain Bottom by Botanicare. made by Botanicare. Use as ebb and flow fittings & bulkhead fittings. VALLEY HYDROPONICS. Outlets are available in 1/2" (13 mm), 3/4" (19 mm), and 1" (25 mm) openings.
The gaskets on the bulkheads are too small causing leaks for all but the most exactingly cut holes. I would recommend finding some with largers gaskets. I had to take gaskets off of some 1" bulkheads that I already had to stop these from leaking.