MOD means Modified Devices or Big Electronic Cigarettes. MOD requires bigger e-liquid tank or container and mostly with big cotton usage. MOD is used for flavor and cloud chasing and is better with 70%VG30%PG blend.MOD E-liquid Flavors are to be used with LESS NICOTINE DENSITY only. High Nicotine density is NOT recommended. If you are a HIGH NICOTINE user, you may feel free to get what you prefered but we recommend getting 12MG nicotine as maximum density. CONTACT US for any further inquiry or clarifications.