You don't need both comp caps. You don't need either comp cap. You might like them and they might work for you... but you don't need to buy 'em up front.Thank you all for replying as I have been looking Vector and I would buy both comp caps for this as well and yes for that price is a no brainer Also I would like a smaller RDA like the Derringer or Snubnose, STRO OG mini, Thump atty, Hobo V3.1 and more. As there are so many good RDA's out just would like to get a good flavor atty that does not leak and no spit back would be nice too.