This bladder, you can place it on the top of your spa water and zip the cover and all water will begin to flow off the spa. Not only this but the bladder will help your spa to retain its heat and keep the water warmer for longer. power source type: Hand Powered SIMPLE TO INFLATE – Since this hot tub cover has been manufactured to be quick and simple to inflate, it can be used within minutes to keep your hot tub clean and warm. EFFECTIVE MONEY SAVER – This premium cover ensures that tub maintenance is minimal, while the cover prohibits items from the entering the water it also cut downs on the number of filters used Fits to Mspa 6 person square spa. Size: 160*160*29cm (63" x 63" x 11.4").