Designed specifically for the bed leveling screws on the Wanhao i3. A common mod is to add some M3 nuts to the bed for more stability. My package had extra nylock nuts so I replaced the wing nuts with nylock M3's and these thumb screws. A massive improvement when leveling. Specifically designed for these nuts: http://www.amazon.com/gp/product/B001BHLSTI?psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s00EDIT: doubled number of teeth, generally cleaned up modelRegular PLA at whatever settings work for you will be fine