4 is of short pixel pitch. P4 is for indoor use because of its short pixel pitch. P4 is used in SMD3528, which has the features of high brightness, short viewing distance, big size, high definition, and small pixel pitch. SMD has better viewing angle and color mixture and it has a bright future. P4 is used indoor, so it does not need waterproof. There are two best viewing distances of P4 led display because there are 2 ways to calculate the best viewing distance: one is by the pixel pitch, one is by the diagonal. One is the minimum best viewing distance:as short as 2.4 meters, the other is maximum best viewing distance: as far as 54.4 meters. The pixel density of P4 is high which is 62500. So p4 has high resolution. P4 usually adopts scanning. The module compoisition of the PH4 is 32*32, and the module size is 128*128, the cabinet size is 1280*1280.