The Wilkins 350ASTDA is a double check detector assembly (DCDA). It is available in 2 1/2″-10″ sizes and has been in production since 2011. The body is made of stainless steel. The 350ASTDA utilizes a 3/4″ 950XLD for the bypass assembly. Parts are not interchangeable between the 350DA/350ADA and the 350ASTDA.