kfconcept
Please note: our M42 adapter ring could not be suitable for Pentax Takumar Super Takumar Carl Zeiss M42 series(aperture pin does not fully depress, small tabs sticking out), as ours depresses the aperture pin all the way down
There are two types of FD mounts
FD/FL Breech-Mount (with a silver ring, you need to rotate the silver ring when attachment and removal), breech-lock mounts are identified by the silver ring
New-FD Bayonet Mount, bayonet mounts are identified by a red dot next to the lens release button
Here are the steps to install breech-mount version
Operating the adapter