Defender Aden Flint has joined Cardiff City.
The 30-year-old heads to Wales on a three-year contract after the clubs agreed a permanent transfer.
Former Bristol City skipper Flint made 42 appearances for Boro after joining the club in the summer of 2018.
The centre-back, who started 39 Championship games, scored one goal during his stint on Teesside.
Cardiff becomes the fourth stopping point of a professional career that started at Swindon before moving to Ashton Gate, where he clocked up over 200 senior appearances.
Flint will link up with Neil Warnock’s newly-relegated Bluebirds on their return to the Sky Bet Championship.
The defender said: “I’d like to thank the Boro fans for their support last season.
"There’s no hiding from the fact it was a disappointing year and we didn’t achieve what we wanted to achieve, but the club is in good hands with the new coaching team and I wish them all the best for the future.”