The part number governs
A description — "latch needle for a circular machine" — narrows the field to thousands. The manufacturer part number identifies exactly one thing. Everything else on a product page, including the photograph, is a way of helping you find that number. Where you have it, send it and nothing else is strictly needed.
What to send when you do not have the number
The machine brand and model from the nameplate, photographed rather than typed — nameplates are misread routinely. The gauge. The old part, photographed beside a rule so scale is unambiguous. The packaging of the last set, if your store still has it. Between them these are almost always enough.
Why "nearly fits" is not a saving
A part that is close will often physically install. It then runs in a position it was not designed for, wears faster, loads its neighbours wrongly, and frequently damages something more expensive than itself before it fails. The cost of the wrong part is never the price of the part — it is the stopped line and what it took with it. If we are not certain a part fits, we will say so rather than confirm it.