Fiber optic rods and sizes…
eBay rules for buying just the rod materials for cheap. Less than $10 for a lifetime assortment. They typically come in 1.0, 1.5, and 2.0 mm. That is 0.040”, 0.060”, and 0.080” for inch sizes. I found one tube, a red one in my box. It mic’s 0.058” so I’m figuring 1.5mm. I think it was from a FA sight I ordered. You’re welcome to it, but YOUR measurements (3/16 - 4/32”) are 0.125-0.187”, much larger.