These are a bit of an oddball bobbin even by our standards!

They are fairly bog standard P90 bobbins - theres a few nice little considerations in the design (holes for the termination wires, the mounting holes aren't all the way though!) - but the important detail here, is that they're actually 49.2mm! Thats the "true" P90 size! The Imperial Dimension Gibson® used originally, and continue to use to this day.

Now, this is actually quite important - because Gibson® guitars fitted with soap bar P90s use a different "shape" of cover compared to all other guitars! (the radius in the corners is wider and more rounded) - and, unsurprisingly, the Gibson® size covers, are also spaced at 49.2mm! So, any time your trying to mesh a P90 to a Gibson Pickguard, tread carefully! Chances are, you'll need the proper cover, and a pickup thats been designed to go into it.

Strangely, this isn't true of Gibson guitars that are fitted with Dog ears either! They use a 50mm pole spacing, and a Polycarbonate bobbin! They're interchangable with all other Dog ear P90s, so you dont have to worry about getting the special bobbins for those jobs.

Remember too, that there are no 49.2mm P90 bases (that i've ever seen) - but thankfully, the 50mm versions will fit to this bobbin (just remember to use a 49.2mm keeper bar)

Beyond some of the weird quirks in "which guitars this actually fits!" and "why are guitars so difficult!" - its as you expect really. Big wide, but unnervingly shallow area for the coils to go in to, all injection molded so no need to worry about reversing the wiring - just, ultimately, a very weird size!