The old style lowers were harder to adjust. I think most installed them and let them in one postition. They were basicly a round pad on a metal threaded shaft that mounted thru the spring hole. On my truck they were so tight even when the truck was unloaded that they were always engaged. The problem is over time the threaded shaft would snap off. One of mine failed after about 2 years.
The new style lowers are built much better with really nothing to break. The swing/pivot in and out so that makes them adjustable.
I havent seen the old style lowers for sale anywhere in a long time so Im not sure if they are even available to buy.