These LEDs are for installing into mechanical keyboard switches which support the addition of backlight LEDs.
They are compatible with Cherry MX, clear-top Gateron, Kailh Speed, and most other MX type switches.
All LEDs are 3mm in size.
*Note: Long leg of LED is positive, short leg is negative. By convention, the square pad on a PCB is positive, so the long leg should be inserted into the square pad. Some PCBs may be different, so test with one LED first to make sure it works before installing all of them.