The magnetic compass bowl has been made of brass for over 100 years and continues to be made that way. A big leap forward in design marks the John Lilley & Gillie SR4 compass as the best A Class compass available in the market. With a body created out of a polycarbonate compound it does not have the problems that brass compasses have with joins potentially leaking. With compasses filled with liquid any leak can cause an air bubble to appear on top of the compass, potentially making it harder to read. The SR4 compasss completely resolves this problem