The Large Aperture Optical Mount 840-0053-01 has a Ø31.8 mm aperture, while 840-0053-02 on its platform has a Ø51 mm aperture and six M4 mounting holes.
Large Aperture Optical Mounts 840-0053 were designed for precise orthogonal adjustment of mirrors. Mounts have six M4 mounting holes on their platforms.
840-0053-01 has a Ø31.8 mm aperture.
840-0053-02 has a Ø51 mm aperture.