the bindings are mounted to a specific boot, and most of them can move 14mm forward and back. So if your boot is a 314mm boot than you can fit a 300mm sole in and a 328mm sole into the binding without re-mounting them.
Look on your boots, on the side of the boot on the heel of the soul. There should be a 3 digit number there that will tell you the length of your boot sole. You should have about 15mm play in the binding for other boots, but be careful, a different size boot may not be centered on the ski.
hope this helps
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