Terrific rollers. Made a HUGE difference in the door noise. You will love them.However, they are NOT sealed ball bearings. You may want to purchase sealed nylon ball bearing rollers but they cost more.Presently, I am very satisfied with my purchase and the price was great !!BOTTOM ROLLER REPLACEMENT:PS: There is a big deal made about changing the bottom rollers as it can be very dangerous. They are under heavy spring tension when the door is down. However, in my opinion, I have observed when the door is at the halfway up position and the bottom roller is in the center of the curve in the track, the cable tension may be observed to be very minimal. Pull on the cable to confirm this. For me, this was the best position to pop the old rollers out and change them. Some You tube videos suggest bending the track to remove them. However, I did not need to bend the track at all assuming the roller is in the optimal position with minimal cable tension.Great deal and quiet rolling. These were priced great and were a great replacement for the squeaking metal wheels on my rolling door. After a few minutes to drop these into place and a few drops of oil, my door moves so smoothly and quietly that I can' really hear it moving from inside the house. That is a BIG change as I could clearly tell and was often awakened by it before the change. These fit like a dream and work well. I never thought of changing the wheels till I saw a Groupon ad for a door tune-up for $125 which was basically replacing the wheels. I checked amazon.com and ordered these. 10 minutes after arrival, and for about $10 I had the same result.I ordered the new rollers as our original were getting very noisey.We only needed 10 rollers.. but the 12 pack was cheaper and we used our PRIME account to get them quickly.The weight of these compared to the original cheap plastic (no bearings) is significant.You can tell when you hold each one that these are much more sturdy.I used a shortcut found on YouTube to replace the rollers..the whole project took about 10 minutes.It could have been done in 5 minutes.. but I worked slowly.The door opens and closes much more quietly and easily now.I should have replaced them a few years ago.Awesome. What a difference. Should of done this years ago. Literally took minutes following the tips on YouTube,to just bend the track out slightly. The only bracket I had to remove, was the very top, which was easy. Last winterour garage was making all kinds of racket during the very cold weather, and would sometimes hang up. No problemsso far this winter, and it's been very cold. Awesome price too. I think you could buy (2) for about the same price at thehardware store.These are a must upgrade from the stock rollers on your garage door. Good quality for such a low price. Smoothed the motion of my door considerably and will likely extend the life of my door opener. Easy to change but be sure to watch a video or get instructions for the bottom most bracket on your door. That one is hooked to your counterweight spring!Our daughter's bedroom is over the garage. We changed our chain-drive opener for a belt-drive and things got noticably quieter. The next step was to change to the nylon rollers. Now it is quieter than ever. This is a great product at a great price. Two nylon rollers without roller bearings at local stores cost almost as much as this entire package. I loved them so much I bought more for my detached garage where noise is not an issue. The lowered strain on the opener is very obvious with this product.I used these to replace the ten steel rollers on my 25-year-old garage door, while installing a new belt-drive door opener (for some reason this pack of 12 was cheaper than the pack of 10). The combination made it extremely quiet and smooth. Look for the You Tube video from DDM Web Services on how to replace your rollers. Be sure to watch all the way through for a shortcut method (it starts at about 6:15). It worked like a charm.Love them. Works great.