Why have stirrer blades to be „tiltable“?

Only a tiltable stirrer blade can be pulled through a narrow neck.

All BOLA Stirrer Blades have a central bore to fix them on a shaft. It is important that this bore is slightly out of the middle. Otherwise, it would be difficult to draw a shaft with mounted blade through e.g. a NS 29 neck of around bottom flask.

By the way: As soon as the shaft rotates, the centrifugal forces push the blade into the correct horizontal position and optimal mixing is assured. 

Blocked: The blade does not tilt and cannot be removed from the vessel.

How it should be: The blade has an excentric bore. It tilts and can easily be removed from the vessel.