Regular Flex. The Mizuno STG 440 takes a step forward to bring superior low spin performance to your bag. The 440cc pear shape head with a deep face is preferred by better players. An allnew Beta Rich TiLFS face is forged and heat treated creating a lighter faster stronger face than the SAT2041. The CORTECH Chamber features a through slot placed under the heel to provides excellent sole flexing. TPU material in the chamber reduces face stress while dampening harsh vibrations for an enhanced feel and sound.