Page "Cardinal (Catholicism)" Paragraph 74

A cardinal who is not a bishop is still entitled to wear and use the episcopal vestments and other pontificalia ( episcopal regalia: mitre, crozier, zucchetto, pectoral cross and ring ).

Almost all of the prominent priests who were elevated to the cardinalate as cardinal-deacons were near or over the age of 80 when elevated, and so would not have participated in a papal conclave.

For those priests over 80 who became cardinal-deacons and were not ordained to the episcopacy, this is the highest position they can normally attain in the Church hierarchy ( though all cardinals rank above bishops in rank and order of precedence, those cardinals who are not bishops do not have the right to perform the functions reserved solely to bishops, such as ordination ).