Those hoops (half circles) are part of the extensions and allow the saw blade to pass thru without cutting the extensions. If you don't ever see a need for ripping small pieces, probably not worth getting the full set. Just so you know, I've found that the mount mechanism on the large guides blocks some of the measurement scale. I believe I was trying to do a rip 180mm from the blade, but couldn't set the stop because I couldn't see that part of the scale. They aint perfect and not well thought out! --- my opinion.