A quotation is only as good as the specification behind it. These are the five details that let any fastener supplier — including us — come back with exact sourcing options instead of follow-up questions.

1. Diameter

The thread's major diameter, in millimetres for metric screws: M2, M2.6, M3, M4 and so on. For self-tapping screws sold in the Chinese sizing system you will also see numbers like 4.2 — that is the outer thread diameter in millimetres. If you are replacing an existing screw, measure across the thread crests with a caliper and round to the standard size.

2. Length

Measure from where the screw sits — not from the tip:

  • Pan head and button head: from under the head to the tip.
  • Countersunk (flat) head: total length including the head, because the head sits inside the hole.

Small screws are usually 4–30 mm long. If your old screw is 6.5 mm, say so — suppliers will match the nearest standard length and confirm it back.

3. Head type

The head decides how the load spreads and how the screw sits:

  • Pan — rounded head above the surface; the default for small screws.
  • Flat / countersunk — sits flush in a countersunk hole.
  • Socket cap (cylindrical) — tall, strong, driven by a hex key.
  • Thin / low-profile — where headroom is tight.

See Understanding Screw Head Types for the trade-offs in detail.

4. Drive

  • Cross recess (Phillips) — the standard for small self-tapping and machine screws; works with every electric driver.
  • Hex socket (Allen) — takes much more torque; the choice for clamped joints, jigs and frames.

Match the drive to your assembly tooling: if your line already runs Phillips drivers, a hex socket screw adds a tool change.

5. Material and finish

Say the environment, not just the material:

  • "304 stainless" for moisture and visible metal.
  • "carbon steel, nickel plated, indoor" for bright consumer hardware.
  • "carbon steel, black oxide finish, inside housing" for hidden joints.

(Our 304 vs carbon steel and nickel vs zinc guides cover this in depth.)

Putting it together

One line per item, like this:

M3 × 10, pan head, Phillips, 304 stainless, machine thread — 50,000 pcs

or the shorthand many buyers use:

M3x10 pan Phillips A2 — 50k
PA 4.2 x 13, nickel plated — 100k

Add three more things and your RFQ is essentially quotation-ready:

  1. Quantity — even a rough monthly volume ("about 20k/month").
  2. Destination country — freight changes the comparison between options.
  3. A photo or drawing of the existing screw — the single best cure for terminology confusion. Attach it to the RFQ form.

Why this pays off

Every clarification round adds a day. Buyers who send diameter × length, head, drive, material/finish, quantity and destination in the first message get useful sourcing options back in the first reply — and comparing two complete quotations beats comparing two guesses.

Ready to send it? Request a quote — one line per size, photo optional but welcome.