I can vouch for the 30mm as I have one in a f5. all the reviews come back positive on it. I have writen a very amateur review in the equiptment forum
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I did almost go for the 1.25 15mm tho but went for the 30mm in 2 inch instead... glad i did.
they have a cheshire collimator for $45 there that works well to if you need one.