A trip unit wherein one sidewall of a trip unit housing assembly captivates a trip bar is provided. A captivation assembly is coupled, or directly coupled, to a trip unit housing assembly, thereby limiting tolerance buildup. The captivation assembly includes a trip bar bearing cap having a stop feature, thereby limiting tolerance buildup. The trip bar includes a radial stop paddle having hemispherical protrusions structured to contact the trip unit housing, thereby limiting tolerance buildup. The captivation assembly elements are incorporated into the trip unit housing assembly and captivates the trip bar in all but one axis, thereby limiting tolerance buildup and improving repeatability.