5.5mm(7/32")

Bought these based on the recommendation of a reviewer for the bolts I used to install the floorboards. Broke two total which was A LOT less than I expected to. These were a huge time and money saver as I didn't have to go to the big box store and spend a lot more on individual bits.If you are buying these for a floorboard or similar project, well worth it!! Great set of bits!

They are sharp and true. They do have cobalt in the metal which makes them prone to the cutting edge breaking when bound against the last part of the cut. If you are using is a hand drill expect this. I was able to drill though track bolts (grade 8) on the master link. If I kept a close watch on the amount of pressure i was putting on the bit I had no problem with the cutting edge breaking. I never broke a bit except the cutting edge which was my fault,Overall great bit especially for the price.

This is the go to Drill Bit! WOW! 42 Bucks at Lowe's and All 3 of the Name Brand Bits BURNED UP!!! These went right through the Stainless Steel in seconds!!! I so am going to do a YOUTUBE.COM video to show this! The BiG Name Brands owe me some money!! What happened to truth in advertising? These are TOP CLASS!!! Buy em' and don't look back~!

Great Bits for drilling steel plate. I drilled 244 5/16" and 196 3/8" holes through 1/4" steel plate with 4 bits. Went too fast and didn't use adequat oil on the first two. Then I slowed drill down and alternated between cutting oil and 40 weight.oil. Worked perfect.

I drilled 10 holes in 1/2 inch thick 304 stainless with one bit. It was turned at the proper speed and lubricated, not pushed hard. After 10 holes it was starting to dull. Good value in my opinion.

6.5mm and 1/4 are NOT the same size. These drill bits are 1/4 inch, NOT 6.5mm.

I've used every bit in the box and they were all straight. That's relatively uncommon for inexpensive drill bits in my experience... They're fairly sharp and had no issues drilling through the resin I typically am machining. Sharpen easily on my drill doctor once I feel they are getting a little dull. Over all a pretty safe option if you're looking for bits.

These drills do a great job on hardended structural steel and 1/4 plate, dozens of holes on the first bit and still sharp. I use oil and cut a slow speed.