100 mg of THC One of the fastest-acting, most accurately dosed cannabis products available. Mary’s patented gel pens have been reported to be a wonderful accompaniment to the transdermal patches or can be used on their own. Available in CBD, CBN, Indica and Sativa. How To Use The pen is most effective when applied to a veinous part of the body, like the top of the foot or inner wrist. Cleanse and dry skin prior to application. Twist end of pen counter-clockwise to unlock, and depress to dispense a 2mg dose. Effects are typically felt within 15 minutes and last up to six hours.