The real vintage blocks, Fender originals, and blocks like the Callaham won't accept the Bullet ends, the ends stick way out of the block.

Fender® Super Bullets® are one of the world’s
most-popular sets of strings and for good reason.
The German-made bullet end fits precisely into
Fender® tremolo blocks, enhancing sustain and stability.
That means you get more for your money with Super
Bullets®: they stay in tune better and they resonate more.
By the way, the bullet end isn’t just for trem users;
it also enhances sustain and stability on guitars with
string-through-body type bridge designs.