I am looking to replace the sash balancers.

the balancers in my windows look like Anderson window style but I could not find any numbers stamped in the metal. my windows have two height pains. the upper is 27 in. and the lower is 40 in. tall. I have two windows side by side and we will be replacing the balancers in both windows.  Can you tell me what inem numbers you sell to replace the balancers.  Thank You.