The collars that hold the weights in place on the bar are really badly designed and poorly made. They should supply the 20 mm spring locks instead. The dumbbells too have a similar problem. Although the threaded lock on the dumbbells keep the weights in place securely, they are not easy to remove, in case you wanted to add / reduce weights. I replaced them with separately bought 25 mm spring locks.The 25 mm spring locks are a tight fit, but they are easier to work with. Apart from this it is great value for money. The weights are basically sealed plastic containers with sand filled in them. Make sure you don't drop or crack them, otherwise the sand will simply spill out.