This stainless steel sleeve allows the ForwardScan Long Stem transducer to be installed through hulls up to 47.6 mm (1 7/8 inches) thick, and at up to 28 degrees deadrise when used with a suitable fairing block. A self-closing valve allows the transducer to be installed or removed on the water; this simplifies maintenance and allows easy removal to protect the transducer while trailering or storing your boat.