Inventory Tracking of Design & Tees

[Ty123]

I have been trying to find the best way to do this, but I'm having issues. What's the best way to track the tee color and size and also the heat transfer designs? For instance, I sell black tees and I have different designs that are available on black tees. My issue has been what's the best way to track both the tee and the design automatically? Would the design be more important than the tee when tracking? So if I have 50 of one design I would have to adjust the quantity for each size to equate to the 50 designs? Can someone help?