Abstract: A container lid system having a lid body with a drinking aperture, a slider aperture and slider, and a recess located on the underside of the lid body. The slider slides within the slider aperture between a first position covering the drinking aperture and a second position exposing the drinking aperture. Slider may be an assembly with first, second, and third slider members that releasably attach to each other via a post in the first member that extends through the slider aperture and second slider member, with the third slider member attaching to the post and retaining the assembly. Venting functionality is achieved by the slider assembly forming a vent channel with the recess on the underside of the lid body when the slider moves towards the open position. Some versions omit the lid body bottom recess and venting functionality or include a matching container.