You get to customize it in many ways. There's 510 standard or long barrel, 901 standard or long barrel, 5 different colors to choose from, 4 different resistances, your choice of PG, VG or both inside the atomizer.
My preference is a 510 standard, 2.0 ohm, 100% PG.
They suggest using 4.3v on the 2.0 ohm, which is perfect for me. The 100% PG inside the atomizer makes it easier to blow it all out before dripping so I'm not vaping the primer for too long.