A coupling for a roller tube of a window treatment system may include a body and/or one or more compliant members. The body may include a bore through a rotational axis of the coupling. The body may be configured to be received within the roller tube of the window treatment system. The body may define an outer surface. One or more compliant members may extend at an oblique angle from the outer surface of the coupling. The one or more compliant members may be configured to engage a smooth inner surface of the roller tube. The use of compliant members may enable a rigid connection of the coupling to the smooth inner surface of the roller tube surface, without the use of fasteners.