I don't know your ecig
blue foam
And if your cart juice cups are small then you can cut down the cheap precut blue foam for 510 carts from strictlyejuice.com
For my small juice cups I cut blue foam about 3/4 the inner depth and a tiny bit wider - just enough to help keep it from slipping in but not so much that it closes off the holes in the foam. Then I taper the inner end a bit. I am using blue foam in both an M401 (very slim 3-piece) and a Joye 306 cart.
What I like about blue foam is its consistent density - once you cut it right you cannot screw up the density putting it in. It's easy to take out, rinse, pat totally dry. On a full fill I pull it, fill juice cup 1/2 way, insert the foam tapered end first, push it down into the juice (a small smooth unbent paper clip is good), reposition foam at top edge of cup, then top off with 1-2 drops for a small juice cup.