Xicon is a manufacturer of small transformers that are commonly used in open-source e-stim boxes, specifically the 42TL series and 42TU series. They are somewhat hard to source but pretty much the only option in this space.

All measurements performed between the outer 2 pins.

The saturation is measured on the output windings, which is the primary in the datasheet.

42TU series

About 24mm wide. Used in FOC-Stim V1 and NeoDK.

42TU200

DC resistance: $0.50\Omega$, $10.94\Omega$

winding ratio: ~5.0, matches datasheet value

saturation: $25000V\mu s$

42TU400

DC resistance: $0.71\Omega$, $17.04\Omega$

winding ratio: ~8.0, datasheet says 7.9.

saturation: $34000V\mu s$

42TL series

about 15mm wide. Used in various 312 clones, FOC-Stim V4 and zc95

42TL004

DC resistance: $0.9\Omega$, $11.75\Omega$

winding ratio: 5.6. The datasheet says 5.0 and 6.66, I tested 2 batches. No idea why the datasheet isn't self-consistent, but both batches appear to be manufactured to the same specifications.

saturation: $7500V\mu s$

Two different batches

42TL004 ebay knockoff

Sold on ebay, not under the xicon name, slightly different specs. It has the model number printed on the top.

DC resistance: $1.1\Omega$(? not very accurate), $19\Omega$

Winding ratio: 5.0

saturation: $9250V\mu s$