The Siemens QP, QT, QAF, and QPF are the standard "interchangeable" plug-on type breakers used in load centers under several brand names including Siemens, Murray, Gould, and Sylvania to name the most common. It also fits most Midwest Power and Milbank Mfg metering equipment. Siemens plug-on breakers are very similar to the GE THQL and in most cases will physically fit however UL listing may be lost when using Siemens breakers in GE equipment. Always contact the manufacturer of your equipment to verify what devices are approved before installing.
