An interface for use in a 3-d graphics system comprising a parametric modelling unit for modelling objects as high order surfaces, and a polygon based rendering system for rendering polygon modelled objects for display. The reinforcer ring cartridge is a disposable item comprised of an annular backing member releaseably attachable to the reinforcing ring applicator. A computer readable medium is encoded with a program that, when executed, can perform the method for work-item tracking. And, after having stopped the PUH in the neighborhood of a position at which the detection state of the inner circumference position detection unit changes over, the PUH shift control unit determines a shift time period T5 for the PUH when a predetermined operation has been performed.