Split collars have several advantages over the standard grub screw type.
They lock on solidly, they don't tilt, and there is no grub screw damage to the bit web. Most important is the solid lock. If you have ever had depth collars creep or slip on you, you know how much damage can result. Good collars at a good price.
Available as a set of seven in Imperial drill sizes (1/8", 3/16", 1/4", 5/16", 3/8", 7/16", and 1/2") or metric (3mm, 4mm, 5mm, 6mm, 8mm, 10mm and 12mm). Hex key included.