PLEASE help me adjust my neck.

The accused : 2006 Mexican made Fender P bass.

The crime : Seemingly randomly selected size for the truss adjustment.

The verdict : I can't for the life of me find ANYTHING accurate on the internet. The most I did find was 3/16" hex key, and that LOOKS right, but it just doesn't fit.

I have tried every plausible allen key in the house.

Someone please help me out here.

For a Mexican P Bass the 3/16" hex key should be all right?!

As a German all these 3/16, 67/128 are "funny" to me, but a 3/16" should be right. Same on my Mexican Nashville Telecaster ...

Squier basses are made in Asia and they have metric keys with 4 mm or 5 mm.
A 4.5 mm key might work for a Mexican 3/16 as well because 3/16 are 4.76 mm ...

Do you have any metal worker near by? A car service should work as well ...
They have a calliper / caliper / slide sauge / venier calliper and can tell you in 5 seconds which key you need. They will measure the width ...

For a Mexican P Bass the 3/16" hex key should be all right?!

As a German all these 3/16, 67/128 are "funny" to me, but a 3/16" should be right. Same on my Mexican Nashville Telecaster ...

Squier basses are made in Asia and they have metric keys with 4 mm or 5 mm.
A 4.5 mm key might work for a Mexican 3/16 as well because 3/16 are 4.76 mm ...

Do you have any metal worker near by? A car service should work as well ...
They have a calliper / caliper / slide sauge / venier calliper and can tell you in 5 seconds which key you need. They will measure the width ...

Zum glück habe ich eins gestern gefunden. Ich kenne noch nicht ob es 3/16 oder 4.5 ist aber es passt auf jeden fall!

Grandad took the neck into his workshop (he is a woodturner, not a luthier), and came back with a suitable allen key within a minute.
My mind was just about blown, but the bass is back together and better than it was.