A microelectronic package can include a microelectronic element having a face and a plurality of element contacts thereon, a substrate having first and second surfaces, and terminals on the second surface configured for connecting the package with at least one external component. A movable electric arc is employed to fuse more than two stacked fibers for manufacturing a fiber coupler having a small size and good environment stability. A covering system for an article of footwear, includes a themed cover adapted to cover at least a forefoot portion of a foot of a wearer. A perforation is defined in the annular wall between two neighboring rotary blades and adjacent to the leeward lateral surface of a leading rotary blade of the neighboring rotary blades. The at least one datum feature is configured to interact with corresponding datum features of the guide track to prevent improper installation of the pen in the carriage.