Built to work with Cricut® Knife Blade Drive Housing (sold separately) this Knife Blade Replacement Kit lets you cut heavy thick materials like leather balsa wood Cricut Chipboard mat board craft foam and more. This premium carbide steel blade is capable of flawless precision cuts. For more info on blade calibration cutting times materials and more visit help.cricut.com/knifeblade. Due to longer cut times requiring Bluetooth™ connection Knife Blade projects are not compatible with iOS and Android devices. To ensure successful cuts always turn off Sleep Mode on your computer before starting a cut. If Bluetooth connection is broken (which happens when your computer goes to sleep or if you travel out of range) you run the risk of completely starting over.