Wires pass through 13.7mm (0.5 inch) diameter tubes in the meter body, so the meter will accept 1–22 AWG insulated wire. It is important to use stranded wire as well for these smaller sizes - too small of a solid wire will either roll over and not have good contact or could break. Even if you have to splice in stranded wire instead of solid this is preferable for such small size wires.
EKM-15IDS and EKM-25IDS (discontinued)
Wires pass through 9.5mm (0.375 inch) diameter tubes in the meter body, so the meter will accept 2–12 AWG insulated wire. It is important to use stranded wire as well for these smaller sizes - too small of a solid wire will either roll over and not have good contact or could break. Even if you have to splice in stranded wire instead of solid this is preferable for such small size wires.
Please Note: It is always best to physically measure your wire diameter with a caliper before ordering pass through meters or CTs. Ordering a meter that will not fit on the wires, or a CT that will not fit on the wires because it is too small, is one of the most common ordering mistakes.