2mm to 4mm Coupling Hub Hello Customers, we would like to inform everyone that we will not be accepting orders until we fix the issue of disappearing shipping cost from your orders. We are still investigating and fixing the settings so that the correct shipping cost will be displayed in every order. Thank you very much for understanding » All Products » 2mm to 4mm Coupling Hub This copper coupler can be used for connection of 2mm to 4mm shafts of RC toys, boats and helicopters. SKU: OTH27407972788 Price: 0.99 $ Product in stock SSL Certificate Quantity Updating cart... This copper coupler can be used for connection of 2mm to 4mm shafts of RC toys, boats and helicopters. Specifications Length: 20 mm Material: Brass Related Products 2pcs Drilled Plastic Panel – Blue JA12-N20 DC Gearmotor (600 RPM at 12 V) JGB37-520 DC Gearmotor (1280 RPM at 6 V) 20pcs 5x5x10 mm Two Hole Plastic Bar Solid State Relay (250 V, 2 A)