Arena Limited Edition Powerskin ST Open Back Kneeskin (26) Introducing the Arena Limited Edition Powerskin ST LE III Neck to Knee Tech Suit Swimsuit, a high-performance racing suit made with the X-Raptor and the Powerskin ST fabrics. The Powerskin ST fabric guarantees outstanding comfort and quick-drying while the X-Raptor fabric provides excellent durability in chlorinated water.