Zirconia alumina and aluminum oxide for up to twice the life of aluminum oxide wheels Type 27 depressed center wheels are used for cutting off and portable grinding Reinforced design helps provide safety, strength, and straight cuts Resin bonds soften under the heat of grinding, releasing dulled abrasive grains Depressed center wheel for use on angle grinder while preventing gouging of the workpiece Exceed expectations with the extended life of this BlueFire ZA/AO Type 27 grinding wheel. Its advanced zirconia alumina and premium aluminum oxide abrasive blend produces a tough face that can last up to two or three times the working life of pure aluminum oxide wheels. This wheel's 1/4 inch central depression gives it just the right shape for a convenient 30-degree angle grind for light-to-heavy duty jobs. Useful across a range of applications, this versatile grinding wheel for your right angle grinder is ideal for working with hard and soft steel alloys, including the 400-series and hard carbon steel mixes. Package of 25.