ABuff 4 inch 100 mm Hole Saw with Arbor, Heavy Duty 38mm Depth Bi-Metal HSS 4 Inch Hole Saw Blade with Positive Rake Teeth for Cutting Soft Metal, Drywall, Plastic, Wood, Fiberboard;

Product Description:
Abuff 4 inches Hole Saw for metal sheet, drywall, plastic pipe, wood, PVC, fiberboard, grommet Hole, recessed light and can light hole Drilling.
Variable depth gullets provide more efficient chip clearance; 4/6 variable pitch teeth for reduced noise and improved performance.
Electron beam weld for stronger, longer lasting teeth.

From the Manufacturer:
The 38mm depth of 4" Bi-Metal Hole Saw is crafted from the highest quality bi-metal. The teeth are attached to a carbon steel body by a process called electron beam welding.
The result is a tool composed of two types of metal welded edge-to-edge - also know as bi-metal construction.
Because the Hole Saws are engineered and manufactured for exceptional sharpness and durability, they will cut much more than wood.
These saws will also cut holes in aluminum, copper, iron, stainless steel and zinc. The hole saws also have a tooth "pitch" that varies from 4 to 6 teeth per inch.
This reduces harmonics and improves performance. Also, the variation in depth of gullets between the blade's teeth provides more efficient chip clearance, giving you greater cutting speed.