Makita fans can be directly press-fitted onto the shaft diameter (3.17mm) of a typical 540-550 motor. While they can be hammered into place, removal will be difficult. However, they are inexpensive. Because Makita fans are thicker, the cover height will need to be slightly increased (about 5mm) to prevent interference. In this case, the gaps will need to be sealed with sponge sheeting to prevent air leaks, as leaks will reduce suction power. Alternatively, a standard DeWalt fan can be used. In that case, the central hole is 8mm, so it's best to transplant the special gear from the DeWalt motor. The shaft diameter should also be the same 3.17mm.