With the 53rd pick overall, the Boston Bruins selected Jack Studnicka a center from the OHL Oshawa Generals. 

Studnicka stands at 6'0 and weighs in at 171lbs. The 18 year old has 52 points in 64 games last season. 

From AllAboutTheJersey.com:

Jack Studnicka is a taller Canadian centerman hailing from Tecumseh, Ontario. Elite Prospects has him standing at 6’1” and weighing only 170 pounds. Given his height, and that he is not a major top prospect, most likely he will want to bulk up and use his size to his advantage in the upcoming years. At this point, however, he is certainly a prospect with some room to grow, both in terms of his game and his size.

Over the last two seasons, he has played his junior hockey for the Oshawa Generals of the OHL, playing quite well for his team this past season. He has an older brother, 22 year old Sam, who has been a decent junior player but never took his game to the next level. Jack is looking to do so by being drafted this year.