Explanation

Intermediate filaments have a diameter of about 10 nm,

Which is intermediate between the diameters of the two other principal elements of the cytoskeleton:

1. actin filaments (about 7 nm) 
2. microtubules (about 25 nm).

Additional informational:

The intermediate filaments are not directly involved in cell movements.

They appear to play a structural role by providing mechanical strength to cells and tissues.