Understanding CubeSat sizes
P-POD can accommodate up to three 1U CubeSats
To date, only 1U & 3U CubeSats have been built / launched
X-POD (SFL/UTIAS version of P-POD) also 3U
P-POD might be extended to 5U for ESPA ring use
CSK available in 0.5U, 1U, 1.5U, 2U, 3U sizes
PCBSat (concept) ca. 22mm (0.2U) thick.
MAST was a 3U that separated into three CubeSats of different shapes and sizes