I've found these to be incredibly handy when bleeding brakes. It's a bleed screw with a check valve... makes it a 1-person job.
I ended up with an extra set... take 'em off my hands.
In a quick look at the application listit looks like they fit the rear discs on NA and NB Miatas, most pre-90 RX7s, early 911s, 914s, 944s, just about any toyota, volkswagen, or BMW...
I can't guarantee the accuracy of their application chart, but an M7x1.0 bleed screw is apparently a pretty widely used metric size.
So: I have 4. The price from the manufacturer is $7 ea plus shipping.
I'll sell for 2/$12 or 4/$20; shipping included.
Matt