Hinge Pin Lower 4×63.5mm (2) / These tough steel Hinge Pins are the perfect spare part for your RC tool box. Key Features: Strong steel material for long-lasting durability, 4mm Diameter, 63.5mm Length, polished finish for silky-smooth suspension action. What’s In The Box? 2 x Hinge Pin Lower – 4 x 63.5mm. To be used in conjunction with #ARA320658 and either #ARA320652 and #ARA320653 or #ARA320655 and #ARA320656.