Rust-proof stainless steel constructionPost on bottomThis commercial kitchen sink strainer assembly by Gridmann is constructed from rust-proof, heavy-gauge stainless-steel and is perfect for use in any commercial kitchen, laundry, janitorial, or industrial garage sink. It fits 3-1/2 sink openings (overall flange diameter 4-1/2) and has a drain connection made to fit a standard 1-1/2 tailpiece/trap. A post on bottom of strainer allows it to be raised for draining water, or dropped for a tight seal.California Residents: WARNING: Cancer and rep