Electronics Transformer Core UF86A Inductor Ferrite Core Ferrite Bead MnZn PC40 1pair per lot

This thing is bigger than I imagined, which is totally fine by me. Al seems to be very close to images ~3900 nH * turn^2. Definitely designed for the not super high frequency range, which is fine, but be awear that over ~100 kHz you may run into issues, as the number of turns you'll need to avoid saturation will also give you a pretty high inductance/impedance. The cross sectional area of the core is massive, so as long as you're not switching more than a couple hundred volts, it should still be possible to work as needed. Could also just tape over the spot where the two core pieces touch to give yourself a little air gap as well. Tons of options with a beast like this.

I'm planning on building my own flyback transformer with this beast and I'm very excited to try it out!