Dual flush

Cool. You should give us the link here.

most all the 1.6 units work this way by default. You just hold the handle down for more water.

I have one of those dual flush kits in my circa 1984 American Standard Plebe toilet. The #2 flush works well, but the #1 flush not so well. I have to hold it in for a few seconds to keep it flushing and most times the toilet paper comes out from hiding. I'll keep it because I know what to do, but this toilet is in the half bath on the main floor that quests use, so they are instructed to use the full flush whether it is #1 or #2

We had one like that back in the 1950's that my father fixed with a straight wire when the chain broke. We saved water with it for years. It would stop flushing when you let go of the handle. The old handle arms were heavier back then, not like the cheap plastic ones now. Whey you let go of the handle it would stop flushing. What kid has time to stand there and hold the handle? Saved lots of water; until the flapper went and since they come with a water wasting chain, it was finally fixed.

That's because the #1 flush is not adjusted properly. On mine, the blue float has to be half an inch under the tank water level to work right. It helps to read the directions.

most all 1.6 toilets will put out almost twice as much if you hold the handle down. The dual is already there, you just have to know how to use it.