I had a bottle of Bulldogs, bought on site and they were fine in my G&G, but jammed up the glock. Some are misshapen and not perfectly spherical, mis matched weights and covered in a horribly tacky release agent.
Once they have been washed they do become a bit more consistent. The release agent and hop up rubber don't interact well.
However they are reasonably serviceable if you don't expect too much of them.
[Addendum] I wil not buy any again, they were fine as a pinch, with the bog standard cm16, in a high cap where you can overkill to make up for inaccuracy, but any decent hop up unit, TBB, or if you actually want the shot to go where you aim there are much much much better options for not a lot more cash.
ASG Blasters are the minimum and BB Bastards get my money everytime now, even in my DE shotty.
I also highly rate the P&J Bios from Taiwangun.