There is presented a casing arrangement for a gas turbine engine. The casing arrangement includes a plurality of tip treatment bars extending between a pair of spaced-apart annular supports, with each tip treatment bar being elongate and supported at each end by a respective support such that each end of the bar is received within an opening formed in the respective support. At least the ends of each tip treatment bar are tapered in transverse cross-section so as to have a wedge-shaped profile, and the openings in the supports have a complementary tapered shape for receipt and retention of the bar ends therein.