Blues North team manager Nigel Way said; "It has been a really decent start for us, especially as we made a conscious decision to lose every one of our squad members in the opening three weeks.
"However, they don't come any more difficult than an away game against the Ospreys, so we will need to be at our best."
The Ospreys, having been pushed all the way by RGC 1404 and the Scarlets in their opening matches, swept aside Blues South last time out and will hope to make it four in four. Team manager Graham Court said; "From the moment the final whistle sounded last week, the boys have been looking forward to this one. It should be another great advert for the competition."
The other game at under 16 level sees the Scarlets take on the Dragons at Parc y Scarlets with the former seeking a first win in three games. The Dragons, who have won two of their three games, are looking to build on their somewhat fortuitous 22-19 victory over RFC 1404 at Rydal School on Sunday.
At under 18 level, the unbeaten Scarlets make the long trip to Newbridge to face a Dragons side whose only game this term brought them a 27-16 victory in North Wales.
Wayne Pugh, the Dragons team manager said; "It was disappointing when we lost our first game to the weather, but equally satisfying to go north and beat RGC 1404 with a bonus point."
They will have their work cut out against a Scarlets side for whom outside half Jordan Williams has been in outstanding form. Team manager Rob Evans said; "It's never easy to go to the Dragons and get a win, but we have started the season well and will travel to Newbridge with a degree of confidence." The Dragons have plenty of fire-power behind the scrum with Luke Rogers, Hallam Amos and Mitch Starr the pick of an outstanding back line.
Last season's winners, the Blues, entertain the Ospreys at Cardiff Arms Park with both sides boasting a 50 per cent record. The Blues, who kicked off the season with a 13-try beating of RGC 1404 at Merthyr, will be keen to hit back from their defeat against the Scarlets last time out. The Ospreys, who lost to the Scarlets on the opening night, redressed the balance with a resounding 86-7 victory in North Wales.
Ospreys under 16: A Rowlands; A Bidwell, L Popham, J Thomas, D Howells; J White, T Maggs; L Jonathan, M Parmenter, G Stone, R Morgan, A Williams, J Davies (capt), C Leyshon, C Davies. Replacements: D Owens, C Forshaw, A Beard, J Collier, D Brooks, M Burnell, J Seldon
Blues North under 16: C Lawrence; J Barnett, A Summerhill, G Smith, S Edwards; J Evans; S Clarke; L Crump, A Gibbs, D Lewis, A Luxton, M Jeczalik, B Llewellyn, J James (capt), T Samuel. Replacements: N Evans, J Smedley, A Panniers, L Davies, J Harris, S Withers, G Davies
Dragons under 16s: M Starr (capt); J Rowley, H Amos, J Dixon, A Hewitt; L Rogers, L Crane; L Garnett, R Thomas, A Jefferies, J Bullen, D Jones, E Whitson, J Ford, R Pugsley. Replacements: K Ball, C Paul, T Sparshott, A Cullen, E Smith, T Senior, J Howell.
Scarlets under 16: J Evans; J Barnes, S Evans, C Woodall, M Davies; J Maynard, G James; B Davies, E Lewis, C Evans, J Helps, A Washbourne, L Watling, W Boyde, L Taylor. Replacements: D Thomas, C Davies, C Randall, T Phillips, G Kenniford, G Rees, J Adams
Dragons under 18s: L Morgan; J Casey, T Ashmead, S Cole, D Franchi; E Davies, J Davies; J Johnson, E Dee, D Goode, J Bartlett, L Randall, J Benjamin (capt), R Stephens, I Jones. Replacements: J Williams, B Edwards, J Everett, G Eldred, J Guy, N Martin, J Pursell
Scarlets under 18: L Treharne (capt); A Evans, S Hughes, D Jenkins, D Morgan; J Williams, C Lloyd; T Evans, T Ball, G Davies, C Morris, D Morgan, S Bennett, D Thomas, C Marks. Replacements: S O'Leary, T Kaijaks, J Williams, O Powell, R Williams, N Setaro, W Lewis
Blues under 18s: R Lovering; H Robinson, C Allen, R Evans, O Rees; R Patchell, L O'Brien; T Davies, J Hopkins, B Thyer, L Connolly, B Roach, J Sienawski, E Jenkins (capt), L Young. Replacements: E Lewis, J Dunning, Z Deere, S Pring, S Middlemiss, G Thomas, L Chalke
Ospreys under 18s: A Wellington; R Thomas, B Roberts, R Evans (capt), A Evans; S Davies, W Batcup; N Smith, E Yardley, D Suter, D Parry, R Hughes, RD Jones, E Williams, M Jenkins. Replacements: J Preddy, S Grabham, O James, M Davies, T Owen, S McRoberts, B Thomas, L Wilson