They are not new... I've been using them for about 3 years. They are awesome but I think they leave the same cut as high lifts. I put them on when grass is at its thickest. The high lifts tend to create a lot of buildup on the deck and the contours are basically a medium lift with a longer cutting edge. They were designed to cut Bahaia grass and to be used in sandy conditions. I also use them with the mulch kit also.
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