The standard LPL Fine Focus Control is typically quite reliable in normal use. However, some institutions have found that with very heavy usage the nylon hub at the core of the assembly may split, which eventually disables the focus knob. For those situations KHB Photografix has developed a heavy-duty version in which the nylon hub is replaced by a brass part, ensuring long reliable operation. Can be used to replace the standard Fine Focus Control on all LPL, Saunders/LPL, Jobo/LPL, and Omega/LPL 4x5 enlargers, and is an option for LPL and Jobo/LPL 7700, and Saunders/LPL and Omega/LPL 670XL series enlargers. Installation instructions are included.