TO hold the quartz capillary and use in centrifugation
Depending on chance, the screw M4.4 or M4.5 both fit well-ish, as long it is reasonably secure, it will be fine.
You will also need this: https://uk.rs-online.com/web/p/rubber-sheets/0205525, cut out a pac-man ghost eater shape of a disc and insert inside the holder, it will create the resistance for centrifuge.