Users need to order a rotor (container for your sample) from Bruker online store. The part number is B200147 (4 mm rotor with 3 Kel-F caps). It is kind of expensive but it can be used many times.
The rotor spins at very high speed (usually >=4khz) during experiments. The acceleration can reach several thousand g. No liquid is allowed in the rotor as it will be squeezed out during spinning. This would contaminate the probe and cause arcing, and make the spinning difficult. A poorly spinning rotor could explode inside the probe and incur thousands of dollars of repairs.