The Novo by Smok is an awesome refillable pod system.
The replacement pods for this device have a 2ml liquid capacity and are available in 2 options; the original 1.2 Ohm pods and the newer 1.5 Ohm pods. The differences between the two are minor, the most noticeable change being that the 1.5 Ohm pods vape a little bit cooler than the 1.2 Ohm.
Salt based nicotine, or salt nic, tends to work the best in these pods. This due to the fact that salt nic liquids are a little bit thinner than normal nicotine which allows the salt nic liquid to work more efficiently in such a small device.
Smok Novo pods are sold in packs of 3.