The MP300 has a modified front window design:
Due to the dual mirror design has a reduced height in comparison with the single mirror of the MP150.
The energy is blocked by a coating on the inside of the mica window.

The MP300 has a modified front window design:
Due to the dual mirror design has a reduced height in comparison with the single mirror of the MP150.
The energy is blocked by a coating on the inside of the mica window.