DIY spot welding pen installation reference. Spot welding is processed manually, the length will be about 8mm wrong, the core diameter is about 2.3-2.4mm wrong, please pay attention to the purchase of friends about the size of the problem. Thank you. Copper tube inner diameter 8mm maximum cable thickness: 4awg (about 7.5mm) Wiring requires some skill, when you need to connect only 7.5mm cable, you need to smooth the line and then turn to a current slowly into the copper pipe (can be reserved for 10-15mm) Spot welding copper core can be installed a 100mm complete refill in 2 sections to use, the tip is threaded tightening fixed type. The spot welding pen can fit a 100 length welding. In addition, it is highly recommended to use hydraulic pliers for tightening. Only in this way can the cable and the pen body be in full and firm contact, to avoid weak contact and affect the welding effect. Hydraulic fixation is not comparable to screw fixation. The spot welding pen is comparable to red copper and not brass. The electrification speed is 3-5 times that of brass, and the heat generation is very small under high current. All s are hydraulically tightened, when a large current passes through, hydraulic tightening is the good, harmless and reliable. Package includes: 1 set Note: 1. Please allow 1-3mm error due to manual measurement.2. As different computers display different colors, thank you for your understanding, the actual product color may be slightly different from the picture.