The key feature of Hong Kong-style milk tea is that a sackcloth bag is used to filter the tea leaves. However any other filter/strainer may be used to filter the tea. Sackcloth bags are not completely necessary but generally preferred. The bag, reputed to make the tea smoother, gradually develops an intense brown colour as a result of prolonged tea drenching. Together with the shape of the filter, it resembles a silk stocking, giving Hong Kong-style milk tea the nickname of "pantyhose" or "silk stocking" milk tea (). This nickname is used in Hong Kong but less so in mainland China and overseas communities.