They appear to look like spiral counter bore step bits.
McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
I know nothing about length or use so you will have to determine if the above are what you are looking for.
I usually find this stuff by looking up different names and looking in Google images until I find what I am looking for then searching in McMaster Carr, msc etc by the proper name.
Usually the generic/ layman's name is heat it will be advertised as to stop people from doing an end run. Then the cheap ones are purchased and sold at a great mark up.
If the 5/16 one is the same length from McMaster Carr then, MC is 1/2 the price of Browe..s.
If you need longer then check extra reach etc along with counterbore or back out in McMaster and narrow your search from the counterbore menu.
Good luck and I hope it helps.