Speaking to glasgowwarriors.org, Glasgow Warriors Head Coach Dave Rennie, said: "They worked excellently together last season. Ryan is a proud Scotsman and he brings the passion you see every time he pulls on our jersey. His ability to relate to everyone is a real strength, and he drives everyone forward on the pitch.
"Callum is a very impressive man. He's got a massive work ethic and is an excellent role model. The two of them are really good mates and bring out the best in each other, and they've learnt a lot from each other too.
"Having the two of them as co-captains allows them to share the responsibility and it worked very well for us last season."