this one pretty easy and so far is working very well. compared to PTB and stock poly and other poly fills that i have used.
what you need
a cart
a piece of heat shrink that will fit right in the cart
and a needle
it pretty simple slide the heat shrink in the cart mark where to cut it i went about 1/8 inch in the cart.
after the heat shrink is cut you need to heat just the tip to make it shrink
once it is shrunk and you have just a little o slide it in your cart
take a needle and poke a hole on the bottom part where the cart clips into the mouthpiece.
now take some polyfill and roll it up in to a tight ball that will fit right in the top part of the cart
then pull out the polyfill and fill the cart up i put about 20 drops in it and don't get any leakage

gray is polyfill
pink is hole
bule is fill area
red is heat shrink
good luck let me kbow how it works.
what you need
a cart
a piece of heat shrink that will fit right in the cart
and a needle
it pretty simple slide the heat shrink in the cart mark where to cut it i went about 1/8 inch in the cart.
after the heat shrink is cut you need to heat just the tip to make it shrink
once it is shrunk and you have just a little o slide it in your cart
take a needle and poke a hole on the bottom part where the cart clips into the mouthpiece.
now take some polyfill and roll it up in to a tight ball that will fit right in the top part of the cart
then pull out the polyfill and fill the cart up i put about 20 drops in it and don't get any leakage

gray is polyfill
pink is hole
bule is fill area
red is heat shrink
good luck let me kbow how it works.