Every drummer knows their model. Very few know that the model means something different depending on who made it.

Where the names came from

Historical factory model numbers, kept because players learned them.

No standards body ever defined a diameter or a length for any of them.

What that means in practice

Two 5A pairs from different makers can differ measurably in both dimensions.

So the same name can feel front-heavy in one hand and springy in the other.

The four numbers instead

Diameter, length, taper length, tip shape. All four are measurable and quotable.

Send a pair you already like and they can simply be measured off it.

What to ask a supplier

For the numbers, not the name. If they can only offer the name, they are reselling.