Q. 1. What is the purpose of the "Cruet set?"

A. 1. "The "Cruets are often sold in pairs, and some styles may be engraved or painted with a symbol or initial to indicate the contents. Most designs have a neck that is narrow enough to pour easily, but wide enough to allow for cleaning. Altar cruets are often fitted with matching stoppers or lids and sometimes come with a matching cruet tray. The designs range from simple blown glass vessels to ornately carved crystal or decorative gold pieces." [Source: https://www.matthewfsheehan.net/church-goods/cruets-trays.html]

The Cruet is "A small vessel used for containing the wine and water required for the Holy Sacrifice of the Mass. Two are always employed. The Roman Missal (Rubricę Gen., XX) directs that they should be made of glass. This is the most suitable material because easily cleaned, and its transparency obviates danger of confounding the water and wine. Other materials, however, are used, such as gold, silver, and other precious metals. In this case it is advisable to have a V (Vinum) on the wine and an A (aqua) on the water cruet, so that one may be easily distinguished from the other. In shape nothing is prescribed, but the vessels should have a good firm base on which to stand securely and a fairly wide neck so as to admit of being easily cleansed. They should have a cover to keep away flies and insects. Formerly the wine for the Holy Sacrifice was brought by the faithful in a jar-shaped vessel. It was then received by the deacon and poured into the chalice, a vestige of which custom is still observable at the consecration of a bishop." [Source: http://www.newadvent.org/cathen/04543a.htm]