I had a round one from Come Quilt with Me that wore out. It got too expensive so didn't replace.
I found a 7" Fiskar square one at Joanns that's about $15. Bought 4 of them, all with coupons. Everytime I find a tool I really like either the price zooms or it goes off the market.
I was taking no chances this time.
I also have a large one by Olfa or Omni (I forget) too big, awkward.