Diamond drill bits that come in packs of 30 are cylindrical. The available sizes are limited to 1mm, 2mm, and 3mm. They don’t have a pointy tip. Their depth of cut is shallow. You will need to hold the tool at an angle to get the hole started. Once the hole is started, you can go vertical upright. Twisted diamond drill bits come in different packs, mixed or otherwise. Available sizes are 1mm, 1.5mm, 2.0mm, 2.5mm. Twisted diamond drill bits have a longer depth of cuts, they have the 120-degree standard pointy tip. You can start upright. Twisted diamond drill bits are a bit more expensive than cylindrical ones.