It's not that they've quit making them in lieu of the more expensive pucks--the other type of puck was a different chemical--calcium hypochlorite--and the manufacturers changed the packaging to a puck without a plastic capsule, which dissolves into mush pretty quickly. The trichlor pucks are the ones that are stabilized, and the stabilizer is what keeps them from getting mushy like the other type.

You can still get both types, but you cannot use the cal hypo puck in an inline feeder.

Janet