The item is a set of 100pcs butt wire crimp connectors terminals, which is made of copper, PVC and tinplate, and it features dual-walled design with polyolefin tubing in outside and hot melt adhesive in inside. They allows visual inspection, prevent corrosion, and provid a waterproof seal. Features - Color: Yellow. - Material: Durable copper, PVC and tinplate. - Suits cable/wire size: 0.1-0.5mm. - Standard crimp and then seal heat shrink butt connectors. - Guaranteed to hold the strong crimps. - Dual-walled design, polyolefin tubing in outside and hot melt adhesive in inside. - Allows visual inspection, prevents corrosion, and provides a waterproof seal. - For best results use a hot air until it reduces in size and the adhesive flows, filling gaps within the terminal.