The tricot is knit just like the t-shirts. Stretch each shirt (gently!) to see which way is 'stretchier'. When you fuse the tricot on the back, if the shirt is stretchier up and down, make sure the extra stretch of the tricot goes back and forth. Clear as mud? It just helps stablized the knit, so it does NOT stretch. (gee..how many times did I type 'stretch'!!?? lolol)