Specification Brand : daier BulletPoint1 : Durable Material: coupling connector is made of fine plating steel, heat and electroplated process make it sturdiness and insulation, striking shaft more stable and easy for installment and replacement. BulletPoint2 : Wide Range of Use:flange coupler is produced based on International Flange Standard, widely used in model shaft connection, perfect accessories for RC Model motor. BulletPoint3 : Size:Inner Diameter: 8mm/0.31inch,Height:13mm/0.51inch,Fixed Hole Screw: M4. BulletPoint4 : Standard Specification:Inner Diameter: 8mm/0.31inch. Cylinder Outer Diameter: 16mm/0.62inch. Cylinder Height: 10mm/0.391inch. Base Diameter: 32mm/1.25inch. Base Height: 3mm/0.11inch. BulletPoint5 : Package included:4Pcs 8mm Flange Shaft Coupling + 1Pcs M4 Mini Hex Wrench + 8 x M4 Fastening Screw. CompatibleGrooveDiameter : 0.125 inches DriveSystem : External Hex ExteriorFinish : Black ItemName : 4Pcs Black 8mm Flange Coupling Connector, Rigid Guide Steel Model Coupler Accessory, Shaft Axis Fittings for DIY RC Model Motors ItemPackageDimensions_Height : 0.39 inches ItemPackageDimensions_Length : 3.14 inches ItemPackageDimensions_Width : 5.11 inches ItemPackageQuantity : 4 ItemTypeKeyword : set-screw-couplings Manufacturer : daier Material : Alloy Steel MetalType : Alloy Steel ModelNumber : 8mm NumberOfItems : 4 NumberOfPieces : 3 PartNumber : H1018 ProductDescription : Parts for RC Airplane Boat ,DIY Model. Perfect accessories for RC Model motor, etc.