A golf ball's cover material sets how much it spins and how it feels at impact — the two dominant options are cast urethane and ionomer (often branded Surlyn). Urethane is softer and grips the clubface grooves longer through impact, generating higher spin on wedge and iron shots for better stopping power on the green; nearly every tour-level ball (Pro V1, Chrome Soft, TP5) uses it. Ionomer covers are harder and more durable, producing lower spin off the driver — helpful for players who slice or hook, since less spin means less curve — but sacrificing greenside control and touch. Multi-piece balls layer cover, mantle, and core independently, so cover choice mainly governs short-game spin while the core still drives overall compression and ball speed.