This serum contains a high concentration of Vitamin C to support skin health. Brand: Obagi Product Name: Vitamin C Serum Model Name: 25 NEO Volume: 12ml Features: High-concentration Vitamin C serum New, unopened How to Use It is recommended to use twice a day, morning and evening. After preparing your skin with lotion in the morning and evening, take an appropriate amount (4-5 drops) onto your palm and apply it to your face. About the liquid color Due to the nature of the ingredients, Obagi C25 Serum may have variations in the color of the liquid. The color range varies from colorless and transparent to yellow and brown, but this does not affect the quality of the product, so you can use it with confidence. About the sound when opening When opening the product, you may hear a "pop" sound. This is a normal phenomenon when releasing the seal, and there is no problem with the quality. Thank you for viewing. Instant purchase is OK. If you have any questions, please comment.