1. 100% brand new and .2. These couplers can connect motor shaft and hex wheel.3. Made of premium brass material, it is and has long service life.4. There are 4 pieces of couplers in one set that you can use for your DIY project.5. Widely used for connecting toy cars, robots, etc.Spec:Features:100% brand new and .These couplers can connect motor shaft and hex wheel.Made of premium brass material, it is and has long service life.There are 4 pieces of couplers in one set that you can use for your DIY project.Widely used for connecting toy cars, robots, etc.Specification:Material: BrassInner Hole Diameter: 2mm, 3.17mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm (Optional)Screw Hole Size: M4Quantity: 4pcsWeight: 47g60g / 1.7oz2.1oz (approx.)Package list:4 * Couplers