General rule of thumb is that you should try to find the same brand of tube thats in the cabinet now.
However, toshiba farmed out a lot of their tubes to other manufacturers for the USA market, and they have different sizes/depth/ect. So you can have a toshiba tv, open it up and its an orion tube with a toshiba chassis.
It's also a gamble if the tube has a bonded yoke, I've opened up two seperate sets that have the same model numbers and the tubes/ yokes are different. Try to make the best of the tubes we have, a tube can have burn in and still have a lot of life left.