Stuka (pronounced "shtooka") is an ambiguous word for "a thing". Often something you cannot identify or define.
Stuka can mean anything from a small device (cellphone, electric wire) to a piece of heavy machinery.
A stuka smaller than a regular stuka is called a "stuchka". Means: "small stuka".
"Pavel, pass me over that stuka."
"This stuka is extremely useful, Ilya"
"This isn't a stuka. It's too small. It's a stuchka!"