One meter long consists of two steel rods C.P. with cast iron provided with four metal riders two of sliders have transferees motion with two lens holder & needle.
(a)OPTICAL BENCH: Same as above but both rods of steel C.p. (b) OPTICAL BENCH: Same as above but both brass covered pipe inside steel rods. (c)OPTICAL BENCH: Same as above but both stainless steel rods.