All my coils are built with 26ga. Ni200 wire @ 0.09 or 0.10 ohms, 3.5mm ID with a 9/10 wrap and Ko Gen Do Japanese cotton. They fit perfect on my Kayfun V4 replicas by Tobeco. Excellent flavor, vapor and warm too! Coils and wicks last a long time. I vape anywhere from 70VG / 30 PG to 100% VG juices so the larger ID coil helps to feed the juice better.
I know that some folks don't like to or care to wrap their own coils, but five pre-built coil heads for $16.99 ? I can get two 50' rolls of Ni200 26ga wire for that price and build dozens of coils at 0.10 ohms.