I had two old lenses from a camera I bought around 1997, almost never used them. What a waste of money... until I recently bought an MFT camera and discovered you can use adapters like this one. Seems well made, feels robust, fits perfectly, looks nice and has a useful ring to change the aperture (note if you have an on-lens manual setting you may need to rotate the ring all the way to one side to stop it overriding the lens setting - not an issue just take note). Yes you do have to manually focus however if you are taking pictures of things that don‘t move too fast or if you are pick a point and get focussed before the action and have a small amount of patience that's easy. I have used my 300mm lens which provides excellent images. In the process of setting this up I have discovered two useful things (sorry - I am no photography expert so may seem obvious to those who are) first is that many cameras allow you to zoom into a very small bit of the photo which allows for easy manual focus (I expect this is common - my camera is around 9 years old - check your manual or Google it) second is that if using extreme levels of zoom and your camera relies on in-lens image stabilisation (like mine) then you might struggle with an old manual lens to get a crisp image, if you do then choose a large aperture (small f number I believe - allowing in plenty of light so you can have faster shutter speeds - also producing really nice shallow depth of field - for dummies like me that means a clear subject and soft focus for the rest of the image) and/or use the sport mode on your camera... it's worked a treat for me. Real photographers - apologies for the really basic explanation - however it has worked for me. Happy snapping!
Edit - still using it and still working great. Have bought a few cheap old lenses and great fun to be able to use them with the MFT camera. No idea why people have scored this 1 star unless they think their autofocus will still work with one of these!