The pairing rule
IEC 60320 couplers come in pairs. The even number is the inlet on the equipment and the odd number is the connector on the cord. C14 inlet takes a C13 connector, C20 takes C19, C6 takes C5, C8 takes C7 and C16 takes C15.
The common couplers
C13 and C14 are rated 10 A and carry almost all desktop, monitor and rack equipment. C19 and C20 are rated 16 A and are used on servers, large UPS units and rack power distribution. C7 and C8 are the small figure-eight coupler used on audio equipment and small adaptors, with a polarised variant. C5 and C6 are the three-pin cloverleaf coupler used on notebook power supplies.
Where C15 comes in
C15 shares the C13 shape but adds a notch and a higher temperature rating. A C15 connector will fit a C14 inlet, but a C13 connector will not fit a C16 inlet, because the notch is the key. C15 is what you find on kettles and heated equipment.
Angles and locking
In a rack the useful variants are the right and left angle bodies, which reduce the depth needed behind the equipment, and locking C13 connectors that latch into the outlet so the cord is not pulled out while a neighbouring unit is serviced. Jumper cords with a connector at both ends run from the PDU to the equipment without a wall plug at all.
