The H.S. Strut Ultimate Starter Diaphragm Calls are made of Premium Flex with Infinity Latex, which requires less air pressure to run, producing more realistic sounds. Premium Flex is a superior diaphragm frame assembly created by Hunter's Specialties. Mouth calls made with this patented frame are more comfortable to use and retain their shape and perfect calling pitch. This combo includes the Double D, Raspy Old Hen, and the E-Z Rasp.