Heavy Duty, built to last 1 1/2" Thread x Thread Black Bulkhead by JT Manufacturing

Magnetic holder can fit up to four probes. It's designed to hold pH, ORP, Salinity and/or Temperature probes. It has a magnet on the back-side, and can be easily installed on sump walls, baffle dividers, or aquarium walls. Magnet can successfully hold to aquariums with walls up to 3/4 inch thick, acrylic or glass.