What is this part called?

[Spirit of 76]

What is the name of this part that the springs hook on to?

[JOLLY]

Tremolo block.

[ItsaBass]

^ Yup, or vibrato block.

[eclecticsynergy]

Also referred to by some as a tone block. But trem block is the most commonly used term.

[dave74]

"sustain block" is also used,,,,,,,,but I say trem.

[Spirit of 76]

Great, thanks everyone!

[ErikH]

I've always known it as the sustain block.