The present invention provides a diaphragm carburetor wherein heat transferred from the engine to the carburetor through the insulator is reduced to lower the temperature of the carburetor unit and reduce the occurrence of bubbles in the fuel. A preferred device fits onto the end of an optical power delivery system, and the thermochromic element changes color if the system output is above a defined threshold. The invention includes the ligands in their own right and when bound to a support and the compounds may be used to prepare metal catalyst complexes. The valve body has an inner wall that forms a recess near the inlet. This eyewear allows the user to quickly and easily change lenses or sunglasses.