Why need to use speed boosterfocal reducer adapter?It converts fullframe lenses into APS-C lenses. The advantage is to get the fullfame field of view onto the APS-C sensor.Feature:Increase exposure to 1 stop, and you can use faster shutter speed to shoot an image.Works fine, closely combined with the bayonet smooth, like the original lens.Full manual operation, manual focus, manual iris adjustment can be achieved with body manual exposure, aperture priority exposure, combined infinite focus.Specification:Max. f-stop pass through: 1.4Optical design (lensesgroups): 43Focal length extension: 0.7xImage diameter (mm): 28.5Bayonet front: 135 full frame lensNote:You must set the camera to Shooting without lens mode to ON before use.Avoid direct shooting to light sources, or otherwise blue spot occurs.Compatible with:M42 LensCanon EOS MCanon M50 M6 M5 M10 M3 M2Package Include:1 X Pixco speed boosterfocal reducerlens adapter1 X rear cap1 X body cap