2mm to 4mm Coupling Hub Shop: There may be some days to weeks delays in deliveries. Thank you 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: 0.94 $ Old 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 JGB37-3530 DC Gearmotor (1600 RPM at 12 V) Aluminum Heat Sink (100x69x36mm) JGB37-520 DC Gearmotor (66 RPM at 12 V) JGA25-370 DC Gearmotor (399 RPM at 12 V) 0-30 V Red Panel Voltmeter