Mastore via Amazon offers the Hotmir Vitamin C Facial Serum 1-oz. Bottle for $14.99. Coupon code "D5EXTL4S" cuts the price to $7.49. With free shipping for Prime members, that's tied with our mention from two weeks ago, $8 off and the lowest price we could find. It purportedly stimulates collagen production, enhances exfoliation, fades sun and age spots, and tightens skin.