A simple question that may be impossible to answer..

[TaketheRedPill]

The m401 carts might be smaller but it uses all the liquid it can get.

Have you tried the Evo cart inserts in the M401 cart? they're larger and easier to handle refilling. Using a 3.75ml dropper bottle (midwest vapor/others) I put an entire dropper full in, add the fiberfil, top with two drops and sit for a second, good to go. (I always change the fiberfil with each fillup)

It's your life. Keep it simple. Choose wisely.
TaketheRedPill