Because the Canon EF mount lens "expects" to be further from the sensor than a Sony E mount lens; this is known as the flange focal distance or the registration distance - a Canon EF lens focuses the incoming light on a plane 44mm behind the lens, while a Sony E lens focuses it on a plane 18mm behind the lens. Extension tubes of 7mm, 14mm, and 28mm lengths can be used individually or in any combination of the three for greater magnification. Lightweight design with metal mounts for durability and longevity. Fits Canon EOS DSLR cameras and all EF/EF-S-mount lenses. 1. As I recall, it's the 25 mm tube that I use with the 55-250 lens. It works well for closer focusing. The lens manual has the documentation that one needs to decide which tube to use. ThrillaMozilla's gear list: Canon EOS Rebel SL1 Canon EOS M6 II Canon EF 400mm f/5.6L USM. Extension Tube EF 12 II. Extension Tube EF 12 II is especially suited for close-focusing with wide-angle lenses. Merchandise type. Need to order more than 10? Learn More. Need help making a purchase? Contact a Sales Expert at 800-385-2155. Mar 25, 2011 07:49 | #1. I have really enjoyed getting into macro photography with my latest acquisition, a Canon EF 100mm f/2.8 Macro. Now I am considering increasing the magnification with a Canon Extension Tube, but my dilemna is whether to invest in the EF 12 II or the EF 25 II. I understand that the difference in the magnification is due Macro Lens Tube Extension for Canon DSLR, Micnova KK-C68 Pro Auto Focus Macro Extension Tube Set for Canon EOS EF & EF-S Mount 5D2 5D3 6D 650D 750D Film Cameras (12mm 20mm and 36mm Tubes) Mcoplus Extnp Auto Focus Macro Extension Tube Set for Nikon AF AF-S DX FX SLR Cameras Vello Auto Extension Tube Set for Canon EF/EF-S Mounts and Lenses. B&H # VEEXTCD MFR # EXT-CD. 442 Reviews. Key Features. Shortens Minimum Focus Distance of Lens. Provides Macro Capability. Full Autofocus Compatibility. 13, 21, and 31mm Tubes. DG-C Auto-Focus Macro Lens Extension Tube Set (12mm, 20mm, 36mm Length) for Canon EF/EF-S Mount Lenses n DSLR Camera 5D2 5D3 5D4 6D 7D 70D 80D 700D 760D 1300D T7 T6i T5i Recommendations Movo Photo AF Macro Extension Tube Set for Canon EOS-M, M2, M3, M10 Mirrorless Camera System with 10mm, 16mm & 21mm Tubes (Metal Mount) SaVKL.