Depended on what type of bulkhead you're using you'll want to get
35mm glass drill bit for 3/4 ABS bulkhead (most common type)
42mm glass drill bit for 3/4 schedule 80 bulkhead
45mm glass drill bit for 1" ABS bulkhead (most common type)
48mm glass drill bit for 1 schedule 80 bulkhead
Never tried the ones off
amazon, always got them from
BRS and had good luck with them. I used the 35 and 45 mm to drill my 40 breeder.