筒子 (tǒngzi): tube; cylinder; tube-shaped obj…

The internet-slang sense (folks / comrades) is a phonetic pun on 同志 (tóngzhì) and a staple of early 2000s forum culture (BBS, Tianya, Baidu Tieba). Use it for 'fellow readers / fellow fans' in casual online posts. Outside that context, 筒子 is just literal: tubes and bobbins.

culture

筒子楼 (tǒngzilóu, 'tube building') is a related word: the long communist-era dorm with one corridor and shared kitchens/bathrooms — a key piece of 20th-century housing vocabulary.