A postless 510 cartridge has no center post: the coil sits in a sintered ceramic bucket with an embedded FeCrAl element. Capless means no press-fit cap — you fill through a self-sealing silicone septum, so the capping station comes off the line entirely. Mono is our patent-pending build of that format. Transparent terpene-resistant polyamide tank instead of glass, peroxide-cured FKM base seal, 510 thread. Sold wholesale to extract producers. Under $1 landed. Free samples at postlesscart.com.