The Ella Low 3 1/2-in threshold Walk-In Bathtub lets you enjoy a luxurious soak in comfort without worrying about getting in or out of your walk-in bathtub or worrying about slipping and falling. Ella Walk In Baths Low Threshold walk-in tub is designed with a 3 1/2-in threshold. The low 3 1/2-in threshold walk-in bathtub is perfect for people with injuries affecting stepping in, out or over bathtub thresholds. Tub Shell is made of high quality fiberglass material with excellent color uniformity, durable gel coat surface, easy to clean high gloss finish, Wall extension kit to fit in standard 60-in opening.