The length of your long 6.5" ruler really depends on the size of your cutting mat. I have an 18 x 24" mat, so I use a 6.5 x 12.5" ruler. This requires me to fold my fabric twice in order to cut it cross-wise. It's always tricky doing that because if it's not straight of grain, I risk creating strips that are humped in spots. If you can swing it, a larger mat would be great with a 24.5" long ruler. I find the 6.5" square very useful. I don't have a lot of specialized rulers, but I do like having a smaller 3 x 6" ruler. Maybe wait and see on the special ones until you find you need them?