When selecting cleanroom shoe covers, it is important to consider the following factors:

Material: 
Look for shoe covers made of materials that are non-shedding and lint-free, such as polyethylene or polypropylene.  These materials will not contaminate the cleanroom environment.

Fit:
The shoe covers should fit snugly over the shoes to prevent particles from entering the cleanroom.

Durability:
Look for shoe covers that are durable and tear-resistant to ensure they last for a reasonable amount of time

Ease of use:
Shoe covers that are easy to put on and take off are essential for maintaining a cleanroom environment.

Additional features:
Some shoe covers may have additional features such as anti-skid or static dissipative properties, depending on the specific cleanroom requirements.

It is also important to consider the cleanroom class and the level of protection required. It is always advisable to check with the cleanroom supplier or standard.