In this article we analyze construction and history of helmets with plated mail aventails, in particulate "Circassian" examples dating from the late Middle Ages to the early Modern times. In total, we present 12 full size helmets and 6 misurka helmets from various Museum and Private collections in Russia, the USA, the UK, Poland and other countries. It is established that aventails with a plated mail are commonly found with various types of Circassian helmets, from the tallest, so called "Tazh", examples, to the flat misurka. Comparative analysis showed that aventails found on "Circassian" helmets substantially differ in design from other plated mail examples used in Europe and Asia, which allows to identify them as belonging to a separate, "Circassian" type. Based on the overall shape, "Circassian" aventails belong to the category of those offering the fullest protection, i.e. up to 59 cm long examples, covering the warrior's forehead, throat, neck and descending upon the chest. In the neck area the opening would be closed by means of a hook. If we are to consider a traditional Russian classification of plated mail as either "kalantar" or "behterets" (i.e. the one in which the plates do not overlap with each other, versus the one where they do), then all known "Circassian" examples belong to the former type. In a typical case, vertically oriented rectangular plates are symmetrically placed in a single row onto the aventails' mail, often with considerable space between them. The shape of plates may way, so that the preference is given to protecting the forehead and temple areas. The number of plates within a single aventail varies between 4 and 12 pieces. In most cases, the plates' surfaces are covered with a thin sheet of silver-copper alloy, decorated with embossed pattern, often covered with the remains of gilding. The ornamental motifs are dominated by traditional Circassian patterns, such as solar signs, most often appearing in the form of a blossoming flower with 7-10 petals, almond-shaped, rounded, heart-shaped "medallions", and swirls in the form of a comma pattern, sometimes referred in the literature as "Ram's horns". The pattern on the plates is typically enclosed within a rectangular "cartouche", and the decorative elements are separated by plenty of smooth, open space. The rings used in aventails found on "Circassian" helmets are of "panzyr" type, i.e. small flattened rings, each interlinked with four neighbors, and closed by creating a protrusion on one of its sides, hole on the other, and then putting them together. The full extent of the area where these helmets were used, remains an open question. It can be stated with confidence that it was employed by warrior nobility of Northwest Caucasus as well as at least the upper classes of the Crimean khanate. It is very much possible that to some extent they were also used in neighboring Georgia, North-Eastern Caucasus and other adjacent territories. The earliest of aventail examples under consideration in this article dates back to the XVII century, and the most recent to the first half of XIX century. Helmets and misurka with plated mail aventails account for about 16 % of the total number of combat helmets of the "Circassian" type, this element is clearly being associated with more decorated examples, many of which are signed to various branched of Girey aristocracy, including Sahin Girey, the son of the Crimean Khan Adil Giray (1666-1671), as well as the last Crimean Khan Sahib Giray (1771-1775). It is possible that the use of richly decorated plates in such aventails, was not so much to improve the protection offered, as much as a conservative reference to the earlier helmet types and by itself a status symbol. It is consistent with the fact that one never finds Circassian suits of mail containing plates, save small isolated oval objects, most likely of talismanic importance.