In a bandstop filter having an input port, an output port and a waveguide connecting the two ports, at least one resonator body is located in the waveguide, which resonator body has resonance frequency above the limit frequency of the waveguide. The guard is comprised of two halves that are hinged together with a stainless steel pin at one end. The conduit contains finely-divided loosely-filled powdered sterile biomaterial and a plurality of powder-contacting clump-disrupting projections arrayed inside and along the length of the conduit between the actuator and the nib. The treatment decreases the sizes of the dots and increases their viscosity. A connection path is in fluid communication with the first chamber and the second chamber. The convex structures are arranged to be able to stably support a male terminal tab, improve electrical connection stability and suppress gold plating abrasion.