The GeekVape Aegis Boost Plus/Pro RDTA is meant to work with the Geekvape Aegis Boost Pro Pod Mod Kit and the Geekvape Aegis Boost Plus 40W Pod System Kit to produce a rebuildable pod system. GeekVape Aegis Boost Plus RDTA has a 4ml volume. The Aegis Boost Pro RDTA is ideal for single coil construction. https://www.vapeuniverse.co/products/geekvape-aegis-boost-plus-rdta-pod?pr_prod_strat=e5_desc&pr_rec_id=15e216ed3&pr_rec_pid=7846687080700&pr_ref_pid=7846694289660&pr_seq=uniform