This portable spot welder is designed for DIY enthusiasts and professionals. Its compact design features an integrated power supply and welding pen, eliminating the need for external components. The welding pen uses gold-plated terminals for excellent conductivity and low contact resistance. It includes a miniature USB charging interface for convenient charging. The unit is well-crafted and delivers reliable performance. It is easy to operate and built for long service life.Operation instructions: 1. Press and hold the power button for 3 seconds to turn the device on or off. 2. After startup, the unit operates in automatic welding mode, delivering one weld every 2 seconds. 3. Press the power button to adjust output power level; blue LED indicates selected gear. 4. Ensure battery surfaces are free of rust and clean. 5. Ensure nickel strips are clean and smooth. 6. The welding tip must make firm metal-to-metal contact to initiate a weld; lifting the tip allows the next weld cycle. 7. Apply appropriate pressure so the welding needle, nickel strip, and battery surface maintain solid contact—avoid poor or intermittent contact. For different nickel strip thicknesses, select the appropriate power gear. Higher power is not always better; test to determine the optimal setting.Model: 401 Charging: Micro-USB, 5V Battery: Compatible with 18650 or 21700 lithium-ion batteries Warning: Do not touch any metal parts of the device body with the welding pen. Color: Black Material: Aluminum alloy Dimensions: Approximately 249.7 × 57.83 × 24.45 mm (9.84 × 2.27 × 0.96 in) Package Contents: 1 × Spot Welder Machine Note: Light reflection and display differences may cause slight color variation.