This is the Axial OCP Rear Full Width Axle Adapter Set.
Works with AR60 OCP axleSteel axles with black oxide coating to resist corrosionAluminum hub carriers
Two Axles, AXIC0775Two Hub Carriers, AXIC0833Four 5x11x4mm Ball BearingsThree 3x5mm ScrewsInstruction Sheet
Short Axle Length: 4.5" (114mm)Long Axle Length: 6.7" (170mm)Diameter: 0.18" (4.6mm)