The T15-D4 is a replacement soldering iron tip designed for Hakko FM-2021 and FV-2027 soldering stations. It features a 4D chisel shape with dimensions of 4.0 mm width and 7.5 mm length, providing a flat, wide contact surface suitable for general-purpose soldering applications. The tip has a 0.5 mm thickness at the working edge, enabling precise heat transfer to components and solder joints. This tip replaces the earlier T7-D4 model and is commonly used in electronics assembly, rework, and repair operations where reliable thermal contact and solder wetting are essential.