Many ballcocks have a piston in an aperture - the dimensional relationship between the two critical components is not stable.
A farmer friend, who has a great engineering mind that runs on 100 ideas a day, looked at an item we already manufacture asked the following question;
"Why don't you do something to solve one of the greatest frustrations of water management in farming? - a better ballcock!"
My friend made a prototype to demonstrate the principle. We then made several and trialled the product - made a few improvements and our first production run was of 50. Now we do production runs in the hundreds. We have a customer whose farm is running one hundred of our SIS ballcock valves.