These are bare PCBs designed to take 12 superflux LEDs. They are fibreglass board, not cheap phenolic resin, and have green solder mask and white printed overlay.
They measure around 300mm x 14mm and are configured in four groups of 3 LEDs, each group having its own current limiting resistor. The boards can be cut into halves and quarters and each section will still run from 12 volts DC.
These boards are designed to aid in heatsinking the LEDs, with large areas of copper for each LED, so you can use superflux LEDs rated up to 100mA in these boards.
Note: does not include LEDs or resistors.