What are "Kosaros"?
Rashi: They are balls.
Radak citing Targum Yonasan: They are crowns.
What is "Mutzak"?
Rashi: It is melted [into a mold]. Radak - this is like the pillars themselves were molten.
Here it says that they were five Amos tall. Below (verse 19) it says that the Kosaros were four Amos!
Rashi (18): Each crown was like two bowls that occupied four Amos; the fifth Amah was like a small crown on top. Gra (16, 20) "v'Chosaros Al Shnei ha'Amudim" (verse 20) refers to the small crowns; verse 19 does not count them.
Here it says that each was five Amos tall. Below (Melachim II, 25:17) it says that it was three Amos!
Rashi citing Beraisa of 49 Midos, Midah 22: The bottom two Amos of the Kosaros were the same as the pillar. The top three Amos jutted out and had a shape - "Sevachim Ma'ase Sevachah" (verse 17).
Rashi: Below it does not count the bottom two Amos because they were even with the pillar; the pillars were inserted into the Koseres.