Function: 1. Puncture clips allow precise pressure application to puncture the insulation of various wire types and sizes. 2. Cost-effective and convenient design allows for quick removal to expose the puncture tip for sharpening, extending product life. 3. Red and black sleeves provide quick circuit identification. 4. Test clips offer added convenience with their 'in-line retention' feature. Once attached to wires, test leads can be removed for testing elsewhere. 5. Attach to a banana plug, then hook the other end onto the insulated wire. By twisting the red or black end of the clip, the needle penetrates the insulation to contact the conductor. Specification: Probe Measurement: 4mm Please check as much as possible to ensure the item is what you need. Tips: Product may be continuously updated; actual product may have slight differences or color variations due to different batches, which do not affect usage. Material: Plastic Color: As shown Package Contents: 2 x Test Hook Clips Only the above package content is included; other products are not. Note: Light reflection and different displays may cause the color of the item in the picture to be slightly different from the real thing. The allowable measurement error is +/- 1-3 cm.