They suck if you use propane/greengas, I use only the madbull CO2 nades available at airsoftparts. Keep in mind the M.E.D if you are using these nades at 600+ psi it can hurt real bad if fired at close range and also unless you are using the madbull launcher, upgrade your triggers, firing pin and stiffer trigger spring on your launcher to steel. Typically We ran ours at a friendly 400psi for indoors, outdoors we ran it at 600psi for the assholes/bunker huggers and non callers we have a special 900psi rounds.
The red ones are what we call "cherries" Xm108HP the golden ones are our "yellow Dildos" XM204HP HP stands for Hi power these are the only nades you should use they are CO2 capable you can charge these to 800 psi if you want (for those supermen in your field), then there are the less powerfull CO2 nades M92A1 then there are also the all purpose nades the XMPB4 where you can put paintballs in them. If you want more penetrating power then go with the XM993 8mm nades or the slugshot M576, if you want to convert this to HP series just swap the internals and the valves