Since I started quilting I have been using this rotary cutter
Like many of the other rotary cutters cuts are made by pressing down on the blade which pushes the safety rim (the blue circle portion) out of the way. I have found though that when cutting through stacks of fabric (say 6 layers and up) the blue safety rim rides along the fabric causing it to bubble along the edge you are cutting and can mis-align it. If you are cutting with the created strips off the ruler this can be not so much of a problem. But if the measured parts are under the ruler then the layers becoming mis-aligned are those you need to cut next.
Well I decided to look for another type of rotary cutter and found two options. Option one was to go with one where the blade locks exposed. then you have to continually close it when you lay it down or risk cutting yourself if it is left locked open.
Option two was to go with the OLFA cutters that have a grip handle that exposed the blade and when you let off grip the blade retracts. This is what I chose to get. In fact I decided to get it in two sizes. The 45mm fits the blades I already had and the 60mm will allow me to cut faster on big units.
While I was at it I bought extra blades for each from KAI in tungstun steel. These are supposed to hold an edge longer.
Ready to roll!