A socket set usually includes at least one ratcheting socket wrench and several attachable sockets. You can purchase sockets in different sizes and torques, and in SAE and metric measurements. Depending on your project, you may need different-sized sockets. If you’re buying for one specific thing, make sure you know what size bolts you will be using. If you just want to have a versatile socket set on hand, it is best to buy a larger set with a range of sizes.