This bearing set is a direct replacement for the 420H and 440H helicopter motors for the Blade 400 and 450. The bearing swap is fairly easy if you have the correct tools.
To replace the bearings: First, I removed the e-clip with an X-Acto blade. Next, removed the lower/outer bearing with a small pin punch, a ball peen hammer, and a PVC pipe fitting. The fitting allows the bearing to press out. Then, I removed the upper/inner bearing with a medium-sized pin punch, and a 7mm 1/4" drive socket. The socket, allows the bearing to press out, and it also protects the armature windings from damage.
To insert the replacement bearings, I used an RPM bearing blaster and automotive brake cleaner to remove the manufacturing residue, and lubricated with Trinity bearing oil. I then used a soft-faced hammer and a soft block to press the upper/inner bearing in, and the same socket to press the opposite bearing in. I also used a medium pin punch and a ball peen hammer to ensure the bearings were fully pressed, making certain I was striking the outer bearing race and not the inner race or bearing shield.
Overall, the previous bearings lasted five years, and the replacement cost is 1/10th the retail price of a new motor! So, the bearing set is worth it if you have a few hand tools and some know-how....