Hello,

The answer is Microfilaments.

Microfilaments are cytoskeletal elements which are 3-6 nm in diameter and they are made up of a protein called actin. Microtubules are larger in diameter about 20-25 nm and they are made up of alpha and beta subunits of tubulin protein. Intermediate filaments are smaller in diameter. lamins are specialised kind of intermediate filaments found in nucleus.

Hope this helps, Good luck.