The Canon EF25 Extension Tube is an intermediate ring for close-up photography. By attaching the ring between an EF lens and a camera body, high-magnification photography becomes possible. Magnification differs depending on the lens used with the EF25, but magnification of .7x or more is possible. You can also use the EF25 in conjunction with the Canon EF12 Extension Tube for an even greater amount of magnification.
The EF25 is equipped with eight electronic contacts, permitting the retention of all normal AE functions. The EF25 is compatible with all EF lenses, except for the following: EF25mm f/2.8 Fisheye, EF14mm 2/2.8L USM, EF20mm f/2.8 USM, EF24mm f/1.4L USM, EF50mm f/1.0L USM, EF17-35mm f/2.8L USM (at wide angles), EF20-35mm f/3.5-4.5 USM (at wide angles), TS-E 45mm f/2.8, and other AF-only lenses.