I am selling my GENUINE Apple MagSafe 2 power adapter (for the MacBook Air, older version, NOT USB-C) - see the picture for what the attachment looks like, or Google "MagSafe 2".
It works great and is the newer MagSafe which doesn't have the problem where the cord breaks all the time like the old MagSafes. It has been in my book bag with pencils and stuff and has the scuff marks from that - for the cosmetic reasons it's less than half the price of the selling price for the same part $79. Definitely much more reliable than the cheaper knockoffs you can get on Amazon.
My old Mac Air was stolen, and I replaced it with one that charges with USB-C, so I no longer need this one.
It also works with MacBook Pro - I have tried this - the sellers at the Apple Store told me that it may charge the Pro a little more slowly since it is only 45W, but it is a little more portable than the Pro charger.