Shaped like a tube or a can, with a round cross-section and straight sides.
“The main body is cylindrical, kind of like a thermos, but with strange bumps on the side.”
“It's a cylindrical object about the length of my forearm.”
Since Task 8 objects are often odd household or mechanical items, 'cylindrical' precisely describes tube-like shapes such as a canister or rod without needing extra words. Practice saying it clearly beforehand, since it can be tricky to pronounce under exam pressure. Use it early in your description to set up the overall shape before adding smaller details.
Synonyms: tube-shaped, cylinder-like, rounded