This is a very thick grease for use on slow-moving or single-action plastic-on-plastic, plastic-on-metal or rubber-on-metal components, such as O-rings on pistons. Roughly the same consistency as peanut butter, it won't drip, and will resist flowing when squished under pressure.
This is a pure thick silicone grease, nothing really special about it. Just comes in a handy little pot, which is good because you won't need much of it!
In the KC-02 (or G5) this has a very specific application - for lubricating piston O-rings and parts that are exposed to escaping gas pressure.
You can apply a very thin wipe of this grease to the top of your gas routers on your magazines so they slide and seal better against the cylinder, but don't apply too much or it will get carried into your hop and barrel.
It is so thick, it will not be easily displaced by gas pressure, and will not freeze like an oil or thin spray lubricant would.
You should apply a thick film of this grease evenly to the inside of your cylinder with your pinky finger. You do not need to apply any directly to the piston or O-ring, it will pick up all the lube it needs from moving in the cylinder. Excess lube applied to the piston risks blocking the ports and causing an inconsistent gas seal. Just grease the cylinder itself.
Using a thick silicone grease is especially important for the V2 RW piston in the KC-02 as the smaller O-rings are more prone to being ejected off the piston if not correctly lubed. Thin oils and sprays get blasted out of the cylinder by escaping gas, or freeze, which leaves dry spots in the cylinder which pulls the O-rings off the piston, jamming the gun. Every single case of O-ring ejection we've seen so far has been through incorrect lube in the cylinder. I don't care if you've been using vegetable oil for years with no problems, I'm now telling you to use this instead.
A single 20ml pot of this will last you a long time as it has such a limited application in airsoft - just for piston O-rings.