An adaptor for an end effector is disclosed. The adaptor can include a staple cartridge having a plurality of staple cavities and a plurality of staples positioned in the staple cavities. The adaptor can also include an anvil plate comprising an arrangement of staple-forming pockets that differs from the staple-forming pockets in the anvil of the end effector. The arrangement of staple cavities in the staple cartridge can correspond to the arrangement of staple-forming pockets in the anvil plate. Additionally or alternatively, the staples in the staple cartridge can be misaligned with the staple-forming pockets in the anvil. The adaptor can include a deformable overmold positioned over the anvil plate, and the anvil plate can comprise a stamped metal sheet.