A needle assembly includes a transparent or translucent housing with a fluid inlet end, a fluid outlet end, a flashback chamber, and a venting mechanism therebetween. A first image and a second image may be identified for display on a client device. The transmission rate at the central area of the gradient filter layer is smaller than the transmission rate at the edge area of the gradient filter layer. The present invention also jointly uses fingers that are suitable for rapid transport of blank materials that, after processing, are molded and have rigidity. In the engine in which a carburetor is disposed on the side of the cylinder, the starting fuel supplying apparatus and a thermo-sensitive member attached to the carburetor are disposed on the side of the carburetor close to the engine. The materials for the contacts and pedestals are selected to be magnetically soft, electrically conductive and have a low AMR signal.