The SAMSUNG ML 1666 pressure roller, also known as the lower fuser roller, is a rubber-coated component in the printer's fuser assembly responsible for applying pressure to the paper as it passes through the hot fuser unit. This action helps bind the toner to the paper, creating a permanent image. It is a crucial part of the fuser unit, which is subject to wear and tear and may need replacement to resolve issues like streaky or unclear prints.