Maxfli U/4x (One Dozen) The U/4x is Designed with 4-Layers Featuring a Firmer Core, Dupont  HPF 2000 Inner Mantle, Lower Spinning Outer Mantle and Cast Urethane Cover Extra Large Firmer Compression Core provides lower driver spin for longer carry distance, yet maintaining a soft feel Ionomer Casing Outer Mantle provides high MOI with lower spin on approach shots Dupont  HPF 2000 inner mantle reduces side spin for more forgiveness and better accuracy. Piercing, 336 dimple pattern for lower trajectory. The U/4x is engineered with Spin Gap Technology