Both the Dutch defender and Portuguese forward are 6'4", and Brown has revealed that height was something that the Celtic Park outfit might have lacked last season.
The 28-year-old told the club's official website: "The new lads seem friendly, and it is good to have them in. It's good to have some height in the team, we've maybe missed that.
"They seem lively around the training ground and that is the main thing. There are a lot of games before the Champions League qualifiers, so that will help us get used to how they play."
Van Dijk has represented the Netherlands at Under-21 level, while Balde arrives after scoring nine goals for Vitoria Guimaraes.