RC enthusiasts, if you're dealing with worn out bearings in your HPI RS4 Pro 4, this FastEddy bearing kit has everything you need to get back to smooth, fast running! The kit includes all the essential sizes: (4) 10x15x4, (2) 3x6x2.5, (4) 4x7x2.5, (12) 5x10x4, and (2) 5x8x2.5 bearings. Now, fair warning - depending on when your particular model was manufactured and any hop-ups you've installed, your bearing needs might vary slightly. FastEddy really knows their RC stuff though, and they try to keep these kits updated with the most common configurations. The bearings are sealed to keep out dirt and grit that can ruin your performance. Before ordering, it's always smart to double-check your specific setup to make sure you're getting all the right sizes. But if you've got a standard RS4 Pro 4, this kit should have you covered. Installation is straightforward if you're comfortable working on your RC, and the quality difference in how your car runs after replacing worn bearings is night and day. Smoother rotation, less resistance, better speed - it all comes down to good bearings!