Junjin Spare Parts SEALING KIT J407360

This Junjin SEALING KIT J407360 is a direct-fit replacement for specific boom cylinder applications. It’s not a universal set—each seal is cut to match Junjin’s original groove dimensions. You’ll see that right away when you lay it next to the old kit.

Inside the box you get all the necessary U-cups, O-rings, back-up rings, and dust wipers. No extra pieces, no guesswork. We’ve seen some guys try to mix brands; that usually leads to a second rebuild a week later. This kit keeps it simple and correct.

The main rod seal is a polyurethane compound with a higher durometer than aftermarket generics. It handles the spike pressures common in concrete pump or breaker circuits. The wiper has a sharp lip design—helps shed mud and grit before they score the rod.

All rubber components come pre-lubricated with a thin assembly wax. That means you don’t have to dip them in oil or grease before fitting. Just wipe the cylinder bore clean, slide the seals in, and button it up. Cuts installation time noticeably.

Factory part number J407360 crosses directly to Junjin’s own service manuals. No modification, no trimming. If your machine’s cylinder is within spec (no deep scratches or egging), this kit will seal tight for a full service interval. Keep one on the truck—it’s a common failure point past 4000 hours.