Disclosed is a device for tensioning and sealing tightening straps of plastics for package tightenings, in which the superposed strap ends are received in a strap channel which is essentially open at a longitudinal outer side and the two faces. A snowmobile in accordance with an exemplary embodiment of the present invention comprises a chassis defining a tunnel, a drive shaft at least partially disposed in the tunnel, and at least one drive sprocket fixed to the drive shaft. The topsides are unconnected to and independent of the rigid hinge elements. The planarizing machine can include a controller that is operatively coupled to the surfacing device for activating the surfacing device at appropriate moments either before or during a planarizing cycle of a microelectronic workpiece. Alternatively, four port electrooptic and acoustooptic tunable filters are formed by replacing the 3-port beam splitters with 4-port directional couplers, where in each of the directional couplers the splitting ratio for TE input polarization plus the splitting ratio for TM input polarization is substantially equal to one. The avatar may be registered in an enterprise and interaction with a service may occur based on the information defining the avatar.