Talk about the NPC.

Made of 50 types of proteins named nucleoporins. Heavier than the ribosome, nucleoporins are arranged in symmetrical octamers at nuclear and cytoplasmic sides, proteins of each octamer are joined by other nucleoporins that form rings at each side. There are radial spooks that project from the rings to the center where there is another central ring. Central ring encloses a central transporter called central plug. Nuclear ring is attached to smaller deeper ring so that the basket shape is formed whereas cytoplasmic filaments project from the cytosolic ring toward the cytoplasm.