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
Members of the WRU Board were invited to attend a training session where sumo wrestlers were being put through their paces and as WRU President Dennis Gethin reveals, the Tokyo visit will live long in the memory.
Representatives from the WRU and the Welsh Assembly government were invited to meet some of Japan's leading businesses. WRU chief executive Roger Lewis and Wales head coach Robin McBryde were among the guests.
Following Wales Under 20's second win of the Junior World Championship over Scotland, a lot of hard work is still required ahead of the Pool decider against Argentina on Thursday. WRU TV took a look behind the scenes.
Wales Under 20 coach Danny Wilson, captain Ellis Jenkins and winger Owen Jenkins give their post match reaction after recording a comfortable win over Samoa in the opening game of the Junior World Championship in France.