This sale is for one brand new Mamiya 645 fit 58mm front lens cap, suitable for use with many 645 and 645AF lenses such as the 80mm f2.8, 150mm f3.5, 210mm f4 and others.
This pinch-type cap is brand new in original sealed packaging, and includes a string that you can use to keep the cap with the lens (if you want to). This is (as far as I can tell) exactly the same cap as used by Canon and Nikon – but in this case is unbranded. The best third party cap I have found.