A gas turbine engine according to an example of the present disclosure includes, among other things, a plurality of blade outer air seals and a plurality of airfoils, at least one of seals and airfoils including at least one cooling passage. The cooling passage includes a first wall and an opposed second wall bounding the cooling passage, a surface contour of the first wall having a plurality of first surface features and a surface contour of the second wall having a plurality of second surface features. The first surface features and the second surface features are arranged such that a width of the cooling passage varies along a length of the cooling passage defined by the first surface features and the second surface features. The first surface features have a first profile, and the second surface features have a second, different profile. A casting core for forming cooling passages in an aircraft component is also disclosed.