I clean my guns all the time, just like all airsofters should, and this is a complete necessity for that. I'm able to keep it on my gear, just to have it with me. There is no way it may leak or spill if it got shot or anything. I really like its sleek look as well. You can even control the amount of oil let out. And look at that price! The only problems I have had are that it will run out a bit quicker than a can, and from what I've seen you can only buy these online. Other than that, the Madbull Penpal Silicon Oil is a great choice. BY THE WAY, IT DOES NOT DEPLOY LIKE A FELT-TIPPED PEN. It squirts out, kind of like a spritzer bottle, but in a single stream. If you want to apply it to your gun properly you will need q-tips.
Good oil quality
Can see how much oil is left
Won't break if shot
Control of oil leaving the pen
It is just amazing, and for that price, why haven't you bought it already?
Runs out a bit faster than a can
You probably won't find it at your local airsoft store
Need q-tips or a small rag to apply to gun (but that's how all silicone oil is)