The Arms Park youngsters will start the game as favourites after defeating the Welsh All Blacks in two league clashes and Cardiff secured the league title last weekend after their 26pts to 20 win over Bridgend.
Neath are battling for the runners up position but will be looking to deny the Arms Park side an unique league and cup double in the competitions inaugural final.
Ryan Williams starts at scrum half partnering Dylan Pugh, who contributed so effectively to the semi-final success away to Pontypridd. Wing Andrew Jones returns while the pack remains unchanged.
Cardiff show just two changes from the side which defeated Llanelli in the last round with Darren Ryan selected at centre and lock Tait returning to the side after his recent run in the senior side.
Neath U'21s: P.Thomas, R.Carter, M.Jones, P.Smiriglia, A.Jones, D.Pugh, R.Williams, P.James, A.Matthews (capt), A.Jones, G.Evans, L.Bassett, S.Peters, D.Evans, S.Phillips
Cardiff U'21s: C.Anderson, E.Jones, O.Ashman, D.Ryan, G.Williams, N.Macleod, C.Miller (capt), J.Yapp, K.Jarma, D.Evans, L.Tait, C.Stamatakis, J.Malpas, M.Leach, M.Leaman
Whenever Bedlinog tackle Penallta a massive fixure is guaranteed but this Sunday there will be even more emphasis placed on the two rivals when they contest the SSE Swalec Plate final at Principality Stadium.
Ahead of their SSE SWALEC Bowl Final clash with Taffs Well at Principality Stadium on Sunday, Burry Port share their #FABXV nomination with WRUTV in the search for Welsh rugby's greatest volunteers. Everyone can get involved by sending nominations via twitter to @WRU_Community using the hashtag #FABXV
Cardiff Blues prop Gethin Jenkins and Ospreys centre Ben John look ahead to the first game at Principality Stadium in Saturday's double header which is promising to be a special occasion for all Welsh fans.
Carmarthen Quins Director of Rugby Ian Jones and committee member Jeff Thomas along with Llandovery chairman Handel Davies look ahead to Sunday's SSE SWALEC Cup showdown where both teams are out to prove 'West is best'
SWALEC ambassador Shane WIlliams is looking forward to Sunday's Finals Day where the Cup, Bowl and Plate offers a great opportunity for players and teams to experience the magic of playing at Principality Stadium
Carmarthen Quins coach Richard Kelly believes it is an exciting time to be part of the Scarlets region as his side take on local rivals Llandovery in the SSE Swalec Cup final on Sunday, as WRU TV's Graeme Gillespie discovers