our best Shortfill E-liquids are vape e-Liquids mostly filled in large bottles that have some space to add further a nicotine booster or nic. shot. After adding the nicotine booster to the Shortfill bottle, simply shake the contents robustly. The result is a high VG E-Liquid. A capricious amount of nicotine booster will be required to achieve a 3mg nicotine level. Nicotine boosters are available in varying PG / VG ratios.