This kit contains both the replacement magnetic flap and a replacement o-ring seal for the water flow sensors used in the Bestway, Coleman and Lay-Z-Spa brands of inflatable hot tubs. If your pump/heater unit is displaying an E02 error and you find that your magnet is rusty due to the plastic cracking or other things like the one to the left, you should replace it with a new one as it is the most likely cause of your E02 error. The fully assembled flow sensors are selling for between $50 and $75. Why spend all that money when you can repair this yourself. The part you are buying is a 3D printed version made from ABS plastic with the magnet completely sealed to prevent it from being exposed to the water and rusting yet again. You also receive a high quality replacement silicone o-ring to replace your worn one under the cap.