I’m guessing you watched the first video, the one with a single coil, which, as you said, doesn’t specify those details. However, on a later video ( www.youtube.com/watch?v=uNbL3tRZeMQ ), where he makes some improvements to the whole circuit, there are some details mentioned in the description, such as

Input voltage: 24V Number of coils: 4 Wire Gauge: 24AWG

Coil Current: 13A Coil ID: 1.1" Coil OD: 1.4" Coil Length: 0.5" Coil turns: 200

The final outer diameter is ~2" due to the addition of steel wire to create a magnetic flux guide or “shell”.

FET Type: IRLZ44N On time: ~8 ms at max. speed Energy input per pulse: 2.6J

Ball mass: 65 grams Ball kinetic energy: ~0.52J