I Haven't seen anyone use those, but the website says they don't offer any lifting assistance so they wouldn't really replace a counterweight. There are a few builds on here that used internal springs or external gas shocks to lift and hold the door open. That may be a better option if you don't like the look of a CW, or these will work if you don't need any help opening the door.
The only thing that would concern me with these is how long they'd last in a pit environment, heating up and cooling with fat and soot jamming them up? I've seen similar simpler stays like this on an old van door that is just a pair of curved lengths of steel with the centre cut out to slide over a pin, with an extended section the pin drops into when opened. You then lift the arm out of the pin to close.
Myself, I use the super cheap option. It's called the wife.