The Febco 856ST is a double check detector assembly ( DCDA ). It is available in 2 ½” -10” sizes and production began in 2011. The body is made of ductile iron with a fused epoxy coating. The 856ST and 856 main body are visually identical. Parts are not interchangeable between the 856 and 856ST. The 856ST utilizes a ¾” 719 for the bypass assembly.