The research purpose was to determine the morphometric parameters of the coat in animals of productive age. The objects of the study were Tuvan coarse-haired goats at the age of 3 years (n = 20) from the agricultural enterprise “Uurgai” located in the southeastern part of the Republic of Tyva (Russia) bordering Mongolia in the south. Wool samples were taken from the animals from the side behind the shoulder blade for examination using an optical fiber diameter analyzer OFDA 2000. It was found that the length of the down averaged 6.35 ± 0.45 cm (Cv = 31.6). The down in the studied goats is shorter than the covering hair and in 35% of the animals studied it exceeds the length of 7 cm. As a result of wool studies using the optical fiber diameter analyzer OFDA 2000, it was found that the proportion of down hair (less than 30 μm) averages 80.21 ± 1.57% (Cv = 8.8), with a fairly significant difference between the extreme values from 67.52 to 90.84%. The amount of transitional hairs has critical differences from 2.28 to 19.42% at Cv = 64.6, while in animals with a low content of transitional hair in the staple (2.28–4.14%), the peak of the diagram has a value within 15–17 μm with a correlation coefficient of 0.69. The data obtained allows for the following conclusion: in order to obtain high-quality down with the smallest fiber diameter when breeding native Tuvan coarse-wooled goat, special attention should be paid to the presence of a transitional hair type (30.1–52.5 μm) in addition to the length of the down and its diameter.