"It has been an incredibly difficult period for these out-of-contract players but Harrison, Cameron, Fraser and Callum have been terrific with how they have handled the situation, which is a real credit to them," Carlton's football boss Brad Lloyd said.
"Their contributions to the club, not only as Carlton players but as Carlton people, were certainly valued. All four of them are quality people who really helped to create the sense of unity felt amongst the playing group this year, especially during the months spent together in the hub.
"We thank each of them for their hard work and dedication at Carlton."