BC041: Suitable for brushless motors, suitable for desktop fans, suitable for magnetic coils of 37.5mm. Easy to install and use. Easy to remove and convenient to clean. Small power motor/hair dryer fan blade, motor spiral fan blade, hotel household air duct accessories. BC034: Suitable for brushless motors, suitable for handheld small fans, suitable for magnetic coils of 22.8mm. BC027: Suitable for brushless motors, handheld small fans, desktop fans, suitable for magnetic coils of 37.5mm.