Microbeads are manufactured solid plastic particles of less than one millimeter in their largest dimension.[1] They are most frequently made of polyethylene but can be of other petrochemical plastics such as polypropylene and polystyrene. They are used in exfoliating personal care products, toothpastes, and in biomedical and health-science research.[2]
-Wikipedia
To add to this, the definition of microplastic is less than 5mm. So yes, 1mm microbeads are microplastics.
https://en.wikipedia.org/wiki/Microplastics
Millibeads
Centibeads🐛