Perma-Lock Stainless Steel Impression Trays have a permanently attached button on each handle for quick size identification. Built-in, rounded retention rims reduce material overflow. Fully perforated for maximum adhesion. Heavy-duty nickel-plated stainless steel construction is steam autoclavable. Perma-Lock Full Arch Tray Set with one of all eight full arch sizes: #3, #4, #5, & #6 in upper and lower.