The4 x 15 ft. Ice Equalizer Pillow is the ideal way to keep your pool in good condition in the off season. Ice, rain, and snow can put pressure on the walls of the pool and this easy to use pillow can be used to offset this pressure. Simply inflate the pillow and place under the cover during the winter months. Robelle Since 1973 Robelle Industries has been providing superior, dependable, and affordable swimming pool products. They have painstakingly built a line of quality swimming pool products that include pool chemicals, pool accessories, and everything in between. Robelle is dedicated to finding new product formulations that meet superior standards of pool chemical efficacy and product durability so your pool is safe, crystal clear, and healthy.