Sure, It's a piece of metal (or plastic-like stuff) that you put on the atomizer instead of a cartrigde. It has a hole that goes all the way through it, which is shaped like a funnel at the mouth end. It lets you drip liquid straight through from the mouth end to the atomizer without temoving the tip. This makes dripping easier, since you don't have to remove the cart. Also, since it's made of metal, there's no chance of burning the cart or the filler material. It's almost like sucking on the atomizer without a cart, only you won't burn your lips on a hot atomizer, and you won't get liquid in your mouth.
hth
Thank you for the explanation, which is very helpful. i will look for it here.