To the category: Microscope objectives
SIGETA Achromatic 4x/0.10 - panoramic 4x objective with a numerical aperture value of 0.1 N.A. It is designed for a finite optical tube length and has a standard mounting diameter and RMS thread; the parfocal height measures 45 mm.
The 4x achromatic lens is a must-have for any biological microscope: viewing a specimen with the low-power objective in its working position predates every microscopic examination.