Disclosed herein is an improved cup cover that includes a base having a slit extending from an edge, and a protrusion extending from the base. The locking device includes a ring recess, which is located in the button and is downwardly open in the axial direction, into which the guide sleeve engages in a spring-loaded manner with at least two locking teeth, opposite to each other and forming an axial slot between each other. The ink inlet is located to refill the ink chamber at a position that is radially displaced from the axis of the ink ejection port. The first set of chess pieces are visually distinguishable from the second set of chess pieces. In some embodiments, the through silicon vias land on polysilicon gate structures to prevent notch formation during etching of the vias. In other embodiments, only the vertical support portion is partially formed by the flexible sheet restraining member, and the vertical and horizontal support portions are made of a resilient material having an excellent shape-retaining property.