Ireland fly-half Ian Madigan and Scotland prop WP Nel are among the final additions to the Barbarians squad to face England and Ulster.
Coach Vern Cotter has put the finishing touches to his 27-man party, which boasts more than 1,000 international caps and includes a handful of players with Six Nations experience.
As well as Nel and Madigan, there are also places for Ireland prop Mike Ross, Gloucester's Wales hooker Richard Hibbard and France internationals Yann David, Rory Kockott and Theirry Dusautoir.
Former England international Steffon Armitage, left in the wilderness by his move to Toulon in 2011, had previously accepted an invitation to play.
Bath pair Kahn Fotuali'i and Robbie Fruean will also represent the Aviva Premiership, along with Saracens hooker Schalk Brits, with Fruean one of the uncapped players included.
Ruan Pienaar will line up for the Barbarians on May 28 before switching sides and playing his final game for Ulster in the second game on June 1.
Barbarians squad:
Backs: Horacio Agulla (Castres & Argentina), Adam Ashley-Cooper (Bordeaux Begles & Australia), Yann David (Toulouse and France), Kahn Fotuali'i (Bath Rugby & Samoa), Robbie Freuan (Bath Rugby), Rory Kockott (Castres & France), Ian Madigan (Bordeaux Begles & Ireland), Timoci Nagusa (Montpellier & Fiji), Waisea Nayacalavu (Stade Francais & Fiji), Ruan Pienaar (Ulster & South Africa), David Smith (Castres), Frans Steyn (Montpellier & South Africa).
Forwards: Patricio Albacete (Toulouse & Argentina), Steffon Armitage (Pau & England), Schalk Brits (Saracens & South Africa), Thierry Dusautoir (Toulouse & France), Corey Flynn (Star RFC & New Zealand), Ben Franks (London Irish & New Zealand), Gillian Galan (Toulouse), Richard Hibbard (Gloucester & Wales), Facundo Isa (Lyon & Argentina), Census Johnston (Toulouse & Samoa), Mikheil Nariashvili (Montpellier & Georgia), WP Nel (Edinburgh & Scotland), Mike Ross (Leinster & Ireland), Joe Tekori (Toulouse & Samoa), Jeremy Thrush (Gloucester & New Zealand).