If you have a very level smooth yard with a low loving warm season grass like Bermuda then one and one quarter inches will work fine. If however you are less than perfect in your lawn care then halfway between the lowest and highest setting is going to work the best. The highest setting, three and three quarters is to high for most folks unless they like a rough look to their tall fescue, or just their weeds. So, hard to turn nuts or not try the middle, if you oppose it then try the lowest.