The MR-14EX II Macro Ring Lite Flash from Canon is designed for use with Canon macro lenses for close-up photography. With a guide number 34' at ISO 100 per side, its twin tube design allows each flash tube to fire independently, or simultaneously to provide a combined guide number of 46' at ISO 100. White LED focusing lamps and two types of modeling lights allow for accurate previewing of the light's effect. An illuminated dot-matrix LCD screen lets you make adjustments to the flash in both bright- and low-light situations. The MR-14EX II has 12 custom functions, and supports wireless E-TTL when linked with one or more Speedlite 600EX-RT flashes. The ring flash can be powered by 4x AA batteries or an optional CP-E4 battery pack. This unit is compatible with the Canon EF 50mm f/2.5 Compact Macro, EF-S 60mm f/2.8 Macro USM, EF 100mm f/2.8 Macro USM, and MP-E 65mm f/2.8 1-5x Macro Photo lenses. If using the EF 100mm f/2.8L Macro IS USM lens, the separate Macrolite Adapter 67 is required; if using the EF 180mm f/3.5L Macro USM lens, the separate Macrolite Adapter 72C is required.