The phrase "about which piece" is correct and usable in written English.
It can be used when referring to a specific item or topic in a discussion or inquiry.
Example: "Can you clarify about which piece of the project you are referring?"
Alternatives: "regarding which item" or "concerning which part".
I'm torn about which piece I prefer.
It sees the relationship as a game of chess, with 27 opponents crowding the other side of the board and squabbling about which piece to move.
"I want to include some way at the museum for people to talk about which piece made them feel more like doing something".
In the early days it was easy to try a little bit of everything and be casual, and now we have to plan strategically about which piece of the opportunity we want to focus on".
And a central part of the Taylor experience is that people don't agree about which pieces are his best.
They have various ideas about which pieces are more powerful and so they're more important to protect.
The charges are roiling the genteel world of research archivists, who usually toil in dust-jacket obscurity, and inciting a lively debate about which pieces of the past are worth preserving.
As the narrative expands into the next generations there is a terrible tension about which pieces of Milo's mind – mathematical brilliance, navigational knack, addictive personality – have been bequeathed by each division of his DNA, and with what consequences for those who receive them.
Govan is the one who brought Riggio on the board, who whispered in his ear about which pieces of art to buy for the new museum, who consulted with Riggio every day about the cost overruns and the design changes and the million other decisions, large and small, that arose in the five years the two men were building Dia:Beacon.
'When I'm deciding on the barge's programme, I think about which pieces the audience would enjoy.
As I go deeper into the argument framing, figures, and discussion, I also think about which pieces are exciting and new, which ones are biologically or logically relevant, and which ones are most supported by the literature.
