Yes, I've used the M401 C-E2's which is the type Centraltrade sells. Liberty Flights
sell them in 5 packs. Very nice, although they do seem to divide opinion - there are loads of
threads covering the C-E2's (see the cartomizer technical forum). The ones I have (2.5 ohms ish) do suit the low powered M series
batteries just fine IMO, but put them on a 3.7v
mod and they get too hot and taste a bit off. The standard type is very slightly longer than an M401 mouthpiece/cartridge, holds 0.6ml and for me lasts the life of the battery between refills. You can refill them many times. They do an XL version (1.8ml capacity) which will be much larger.
I have seen some "filler type" M series carto's too, although I can't remember where..