 The vessel was initially envisaged as having a displacement of approximately 500 tons, a speed of at least , and a range of  The opportunity to build a prototype in the place of a cancelled Bar-class boom defence vessel saw the proposed design increased to a 680-ton vessel, with a top speed of , and a range of , armed with a 4-inch gun, equipped with asdic, and able to be fitted with either depth charges or minesweeping equipment depending on the planned operations