This is located in the busiest parts of Mongkok, and it is hard to find. It is in the basement shops and does not have street frontage. So instead of institutional coffee at a brand name place, 18 Grams offers a better premium experience.
For those that like HK style snacks to go with their coffee, they have a decent amount of items to choose from.
This is not a hard core coffee tasting, profile discussing, equipment gazing, and cupping comparison type of place, but offers a decent sit down place to enjoy an above average cup of coffee away from the crowds of Kowloon.