What is Structural Floor Level (SFL)? SFL, full form Structural floor level, refers to the concrete topping or floor screeding’s top surface level. The difference between SSL and FFL is 50 mm. Plinth Height The full form of NGL is "Not Gonna Lie," which is an expression used to indicate that the speaker is being honest and sincere about their statement. Image Source : Social NGL stands for Not Gonna Lie, a colloquial way of saying I am not going to lie, or I am being honest. Find out more meanings of NGL in different categories and countries, such as Natural Gas Liquids, Next-Generation Lithography, and National Guardian Life. What is the full form of NGL ? - Natural Gas Liquids - Natural Gas Liquids ( NGL ) are by-products of natural gas that are extracted as a li