Over Floor pool elements ended up at a person time manufactured entirely of steel or steel alloys. Today, the pool walls remain steel but today maker's like Doughboy and Wilbar (Seaspray Pools) are using resin parts in several of their styles to improve their strength, sturdiness and product longevity. See https://www.profi-poolwelt.de/3-60-x-1-25-m-aufstellpool.html