Professional Products Bolt-In Counterweights.
Bolt-in counterweights are a major plus feature in all of their externally balanced dampers. For example, if you purchased one of their externally balanced dampers and during your engine build procedure, you decide you want to switch to a neutral balance assembly, you don't need to buy a new damper. You simply unbolt the counterweight and you are good to go. Some of their competitors who lack this feature have made claims in some of their literature that bolt-in counterweights are a bad thing because they can "come loose" or "fall out" and "do serious damage." They have sold thousands and thousands of dampers with bolt-in counterweights, and they have never heard of one single instance where a counterweight has come loose or fallen out. It just doesn't happen. So if you have any concerns about this, you can forget about them.
Additionally, professional balance shops really like this feature because if they need to modify the counterbalance weight for any reason, it is much easier to do this with a removeable counterweight than to try to remove weight from the damper itself. They also offer all of their counterweights separately because, for example, some customers might want to switch between a 28 ounce inch weight and a 50 ounce inch weight on a small block Ford.