3810 Tool Attachment Sizing Gauge helps you measure the dimensions of the tools being tethered with Squids tool attachments. Use the sizing gauge to measure the diameters of screwdrivers, hex keys and other small, hand tools when applying attachments such as Squids Hand Tool Slips, Self-Adhering Tape and Cold Shrink Traps (none included). Pre-measured holes allow you to quickly thread a tool sized up to 1/2" through it. Ruler ends measure up to 8" for larger tools. It also measures screw ports on drills, grinders and other power tools, sizing the proper fasteners to attach Squids Power Tool Brackets (not included). Pegs on the end of the gauge mimic the M2.5, M3, M4, M8 and M10 fasteners that come with the brackets. Connecting hole lets you hang the gauge on a carabiner.