U‑shape installation machine—commonly referred to as a fusion iron or fusion tool—is a heat-based instrument used to melt and secure U‑tip keratin glue bonds onto the wearer’s natural hair. The “U‑tip” refers to the curved keratin bond at the extension’s root, shaped to encircle a section of natural hair for strong attachment. Key Features & Functionality Precise Heat Application: Fusion irons deliver controlled heat (usually around 200°F to 400°F), softening the keratin bond just enough to wrap around and fuse seamlessly with the natural hair Amazon Every Market .

Ergonomic & Efficient Design: These tools often feature narrow, pointed tips allowing stylists to clearly see the bond during melting and work with precision, reducing accidental heat exposure Amazon Every Market . Versatility: Many models support U‑tip, K‑tip, flat‑tip, and shrink‑tube bonds, making them suitable for various keratin-based extension systems Amazon Amazon . Salon-Level Durability: Designed to withstand regular professional use—these tools offer reliable performance, durability, and precise temperature control