Steel balls and accessories are installed inside the piston rod. Part Number: 704-586 704-551. Compatible with use for Advantage 400 500 600 Impact 440 540 640 etc. Perfectly replace your accessories without any problems.Please make sure the interchange part number matches the part you are replacing. High quality Piston Rod,New machining process for longer life time. High quality Piston Rod 704-551 and Piston Seal kit,Upper Lower Seals. Complete Piston rod, with ball, cage and retainer inside. NOTE: This is an aftermarket product, not-original. Please make sure the interchange part number matches the part you are replacing. Please check our photos and make sure the part shown looks identical to your stock one. Colour:As Shown Material:alloy steel Package Contents: 1 * Airless -Piston Rod set Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.