Variable Extension Tube 64-85 (51691) Discontinued 1995. 12/97 * Continuously variable extension from 63.5mm to 85mm. * Can be used in combination with other extension tubes or bellows. * Optimized for use with the 135mm Makro-Planar CF f5.6, offering a focusing range from infinity down to 1.15m. Focusing is done by extending the tube. --> Extension tubes must be attached to the camera body before attaching the lens to the tube. When using more than one tube, attach the first one to the camera body and then build out, attaching the lens last. Conversely, remove the lens from the extension tube first before removing the extension tube from the camera body. If using more than one tube, remove the tube closest to the lens first and work back toward the camera body.