Amazon.com Product Description: You can count on DEWALT to produce top quality cut-out tool bits, designed for reliable results in a broad range of jobs. The DEWALT This carbide burr bit is designed with 1/4-inch shank for increased endurance and specially designed flute for added productivity in driving applications. Make sure you use the correct bit for your application.
I went through two of these to cut eight 14" x 6" holes in my 1950's era home for HVAC vents and *barely* made it. The edge dulls quickly when cutting a mix of thick drywall/plaster. A repeated 'plunging/sawing' action was required to get it to cut effectively. It did make a tough job easy but be prepared to buy a few to get the job done. All spiral saws are sacrifical in nature and will lose their edge quick so no surprises here. Three star rating due to misleading description about long life.