Universal joint

A universal joint including:

• a socket including a connecting slot and a assembling structure oppositely arranged, the connecting slot including a plurality of first inner surfaces and a plurality of second inner surfaces, the plurality of first inner surfaces and the plurality of second inner surfaces being different in shape and being alternatively and circumferentially arranged, the assembling structure being configured to be assembled with a first external device;
• and
• a connecting rod including a first end portion and a second end portion oppositely arranged, the first end portion being swingably received in the connecting slot and rotatable with the socket, the first end portion including a plurality of first side surfaces and a plurality of second side surfaces, the plurality of first side surfaces and the plurality of second side surfaces being different in shape and being alternatively and circumferentially arranged, the plurality of first side surfaces and the plurality of second side surfaces facing the plurality of first inner surfaces and the plurality of second inner surfaces, respectively, the second end portion being configured to be assembled with a second external device.