Depends on the Reo, the mini or Grand, for the mini, LR attys of 1.5, 1.8 or 2.0 are great and any delrin drip tips or pyrex will do. The grand can take the 2.0, 2.5 or even HV 3.5 attys. The mini takes AW IMR 14500, (2), the Grand takes 18650's. You can get these from AvidVapor...