The 5+ Vitamin Concentrated Serum by numbuzin is quite popular, with a high average rating of 4.32 and 740 reviews. Many users have reported positive results in terms of brightening their complexion and reducing blemishes. The effectiveness of the product seems to vary among users, with some noticing significant improvements within a few weeks, while others see gradual changes over several months of consistent use.

Regarding the duration, the serum is available in a 30ml bottle. Users have noted that it can run out faster than expected, especially with daily use. Some reviewers suggest waiting for sales to purchase the product due to its price point.