The best socket is the one that fits the fastener properly. Match the measurement system, drive size and tool type before adding a set to your toolbox.
Match the measurement system
Metric sockets use millimeter sizes; SAE sockets use fractional-inch sizes. Check the fastener specification or measure it. A nearby size from another system can feel close while still damaging the fastener.
Check the drive size
The square drive connects the socket to the ratchet or impact wrench. Common sizes include 1/4 inch, 3/8 inch and 1/2 inch. Match the socket to your tool and the demands of the job.
Consider the shape and access
Standard sockets work in many open spaces. Deep sockets help reach recessed nuts or nuts on longer studs. Choose a socket shape that fits the fastener and leaves enough room to work.
Using an impact wrench?
Use sockets specifically rated for impact tools. An ordinary hand-tool socket is not a substitute. Follow the tool and socket manufacturers’ instructions, and wear appropriate eye protection.