Kovar (trademark of Carpenter Technology Corporation) is a Nickel-cobalt ferrous Alloy compositionally identical to FerNiCo 1, designed to be compatible with the thermal expansion characteristics of borosilicate glass (~5×10−6 /K between 30 and 200°C, to ~10×10−6 /K at 800°C) in order to allow direct mechanical connections over a range of temperatures. It finds application in electroplated conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs. The name Kovar is often used as a general term for Fe-Ni Alloys with these particular thermal expansion properties. Note the related particular Fe-Ni Alloy Invar which exhibits minimum thermal expansion.