Aperture Macro Extension Tube Set Adapter TTL and Auto Focus for Canon Camera 3 Pieces 13mm 21mm 31mm Built-in electric pins. Perfect for macro shooting. Support accurate TTL & Autofocus. Compatible with all EF and EF-S Canon lenses. Diaphragm control of the lens can set automatically. All the 3 parts can be separated as one adapter tube to use. Each adapter tube has 8 electronic contacts. Upgraded circuitry to work better with digital SLRs cameras and SLR lenses. With lock pin. High quality and compact. Made ofbrass and Aluminum (not plastic). If the tubes are correctly attached, TTL metering and Autofocus performance will function as usual. When using Non-TTL camera, you must adjust aperture and shutter before shooing to ensure correct exposure. This adapter is used by attaching between camera body and lens of the 35mm single-lens reflex camera. It comes as a set of 3 tubes of different lengths which singly or in combination on makes it usable in 7 different lengths.