Features: brand new and high quality Made of rubber material,which is durable and reliable. Since the failure of this component is mostly caused by the wear and tear of its matching accessories, it needs to be properly handled during installation, otherwise it will be installed poorly or not used for a long for time. This component is suitable for RQ-SX AR-10 caliber machines. This idler snap assembly is the most problematic part for RQ-SXAR-10 movement. This opening is used to avoid damage to the plastic bayonet on the fixed shaft by direct pressure during installation. Specifications: Idler Caps Material:Rubber Hole Diameter: Approx. 2mm/ 0.07 inches Outer Diameter: Approx. 5.5 mm/0.21 inches Thickness: Approx. 1.4 mm/0.05 inches Note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 2 x Idler Caps 2 x spring