Handbook of Liturgical Practice of the Russian Church Abroad
In terms of ‘lesser vestments’, our Church Abroad maintains the old Imperial practice of both the mantia and phelon being worn together on most occasions (during, for example, most parts of a Vigil service where the phelon is appointed to be worn). The Hieromonk’s general attire for ‘lesser vestments’ is his ryassa covered by his mantia, over which he wears the epitrahil (stole) and cuffs. When the service calls for the phelon to be added, this is placed over the top of these other garments.
Photograph in which is visible a monk-priest (in this case, an Archimandrite, at right) in lesser vestments, wearing the phelon over the mantia, which is is the correct practice in the tradition of the Church Abroad.
In present-day practice in other Russian Orthodox traditions, the mantia is removed whenever the phelon is added; but the ROCOR maintains this older practice of wearing both.