The common type of ping g15 driver is surlyn, ionomer, urethane and polybutadiene. Surlyn is normally used as the cover. There are however exceptional cases with Surlyn as a thin outer layer for enhanced velocity and trajectory while exhibiting control with Urethane. Urethane is the softest material used for the cover which encourages spin around the green. Ionomer works great with as a soft cover replacing Surlyn for more spin with g15 irons. Polybutadiene is generally rubber that forms the core of the golf ball.
The construction of a golf ball Now golf ball comparisons can even mean comparing the pieces of a golf ball. Compared to the old balata golf ball, the pieces of a golf ball can vary from two to four pieces. Even the types of pieces vary from brand to brand. Ping features a duo core four piece golf ball in their Tour I series. In comparison with Bridgestone B330 series double mantle layer four piece g15 driver, both are four pieces yet with different constructions.
The good news is, you do not need to bother about the various types of Ping g15 irons. You only need to focus on the core, cover, the layer beneath the cover and the dimples.