The T40 is a coaxial quadcopter - it has 8 x pairs of propellers (rotors) in total - 2 pairs stacked at the end of each of the 4 arms. Coaxial rotors means stacked on concentric shafts, with the same axis of rotation, but turning in opposite directions. Important to note DFH sells them as a pair (2 pieces per pair).
One Pair of Lower CCW Propellers, Counterclockwise, for DJI T40
This is a genuine DJI part, not a third-party part. Please note that third-party parts may void the warranty of your drone and are made from unknown designs and materials. This can change the behavior of your drone, cause it to crash, and or endanger people.