Product Name: Mini Pure Copper Universal Joint Coupling Material: natural copperOuter diameter: 7mmLength: 12.8mmHole diameter: 3mm-3mm, marked both ends of the opening is 3mm, either would be connected to the 3mm diameter shaftSide holes are M2.5 hexagonal screws, a complete of 2Each coupling will ship 2 M2.5 mechanical device rice screws, every single order will only send 1 small wrench.Brass miniature universal joint is beautiful workmanship, copper, appropriate for quite a lot of miniature science model transmission, comparable to mannequin aircraft, antique sailboats, etc.Pack Quantity: 1Pcs