I have four: 60, 45, 28, 18. The 60 I use for batting and lots o' layers. The 45 I use most b/c it has the ergo handle, cuts most everything just fine, and the blades are cheaper than the 60s. The 28 I use for small cuts, like those Marti Michell templates, and geting just one square out of a large-ish scrap. The 18 I bought b/c the LQS promoted it for cutting the Marti Michell templates but it really only does 1-2 layers well and dulls quickly so I hardly ever use it.