In general, Campag put lock rings with wheels, whereas Shimano put them with cassettes.
I think what your friend needs is a 27mm Campag lock ring, e.g. http://www.sigmasport.co.uk/Product/19747/campagnolo-oversize-lockring-27x1-12t.asp
Although you need to measure carefully, as there is also such a thing as a 26mm, plus there are 11t and 12t versions with different flange diameters. Token do alloy 27mm ones for under a fiver if Campag pricing is too rich.
@gbj_tester started
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In general, Campag put lock rings with wheels, whereas Shimano put them with cassettes.
I think what your friend needs is a 27mm Campag lock ring, e.g.
http://www.sigmasport.co.uk/Product/19747/campagnolo-oversize-lockring-27x1-12t.asp
Although you need to measure carefully, as there is also such a thing as a 26mm, plus there are 11t and 12t versions with different flange diameters. Token do alloy 27mm ones for under a fiver if Campag pricing is too rich.