Master Spa Waterfall Pillow X540300 Relax. It's Master Spas. Spa Headrest – Small Waterfall Pillow for 2002 and Older. The Small Waterfall Pillow secures to the side of your hot tub with two pins. The rectangle shape and the durable black material of the hot tub pillow fits nicely in the place of the pillow that came with your Master Spa hot tub waterfall feature. This pillow fits near the waterfall feature of your hot tub and allows you to relax completely in the hot cascade of water. Enjoy your hot tub for many years with this replacement Small Waterfall Pillow from Master Spa.