The LHi 954 and LHi 958 pyroelectric infrared-detectors have been a world standard for more than 10 years. They both are dual element types with FET in source follower connection.  The LHi 954 detector is available in TO-39 housing with standard infrared filter whereas the LHi 958 is the same detector in a TO-5 housing with standard infrared filter.

TO-39 / TO-5 housing
High reliability
Well proven design