The short answer
On CNC aluminum RFQs that anodize then paint, **mask and plug notes** decide which faces stay conductive, which stay bare for seals, and which take color. Silence on **mask map / plug list / paint boundary** is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the blank size alone.
This guide is for buyers packaging 6061 automotive housings and brackets where drawings say “anodize and paint” without a keep-out map. Illustrations use an **Example part** only—not a customer ECU cover. Related notes: [as-machined before Type II anodize](https://3dwk.com/resources/as-machined-before-type-ii-anodize), [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost), [laser marking before vs after anodize](https://3dwk.com/resources/laser-marking-before-vs-after-anodize); here we focus on **paint mask and plug labeling**.
What mask and plug mean for quoting
**Mask** keeps anodize or paint off named faces (ground pads, seal lands, threads). **Plug** protects tapped holes and ports from chemistry and paint fill. Process pages for automotive aluminum ([CNC 3-axis Al 6061 automotive](https://3dwk.com/en/cnc-3axis/al-6061/automotive.html), [CNC 5-axis Al 6061 automotive](https://3dwk.com/en/cnc-5axis/al-6061/automotive.html), [CNC turning Al 6061 automotive](https://3dwk.com/en/cnc-turning/al-6061/automotive.html)) assume finish packs when Type II/III and paint share one RFQ.
Do not bury “mask threads / paint black” in a cloud. Put **TYPE II CLEAR ANODIZE; MASK GROUND PAD A; PLUG M6×1.0 PORTS; PAINT PER SPEC ON EXTERNAL ONLY** on the PDF and RFQ text. Background: [DFM checklist before an online CNC quote](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote).
Cosmetic edges, logos and media blast
If paint stops at a crisp break line, name the edge (and whether a chamfer frames it). Logo pockets that receive paint need depth and mask notes distinct from ground pads. Media blast before anodize—if required—belongs in the same finish pack so blasted faces are not confused with as-machined seal lands. Automotive aluminum process pages assume these finish families are labeled; a single “black paint” line is not enough for a stable estimate.
Under **rates.v1.1** planning, each extra silent finish step is another chance for the band to widen. Put blast / anodize / mask / paint / mark in order on the RFQ.
Sequence: machine → anodize → paint
Say whether paint is over anodize, whether touch-up after laser mark is allowed, and whether as-machined faces must stay bare before Type II—see [as-machined before Type II anodize](https://3dwk.com/resources/as-machined-before-type-ii-anodize). Hardcoat vs Type II changes mask risk—see [how anodize choice changes CNC RFQ cost](https://3dwk.com/resources/how-anodize-choice-changes-cnc-rfq-cost).
Under **rates.v1.1** estimates, mask/plug labor is a finish adder; vague “paint where needed” forces the wide band or **needs_manual**.
RFQ checklist for mask/plug packs
List every masked face by name or balloon, every plugged thread/port by size, paint color/spec reference without inventing cert numbers, and mark order relative to anodize. If only some externals paint, shade a simple boundary on the PDF. Estimators comparing automotive 6061 RFQs look for that pack before trusting a mid-line **rates.v1.1** band.
Threads, seals and ground pads
Tapped holes that must stay free of paint need plugs or mask; sealing lands often need **NO PAINT / NO BREAK** together—see sibling edge notes in [surface roughness Ra callouts that raise quotes](https://3dwk.com/resources/surface-roughness-ra-callouts-that-raise-quotes). Ground pads that must remain conductive need explicit mask from anodize and paint.
Tolerance and inspection traps
Paint thickness on fits without a mask note creates assembly risk. Put dimensional controls on machined faces before paint, and visual criteria on painted zones. Related: [chem film vs Type II anodize aluminum](https://3dwk.com/resources/chem-film-vs-type-ii-anodize-aluminum), [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote).
Illustration 1 shows an **Example part** with labeled mask pads, plugged ports, and paint-boundary edges.
Example part walkthrough
**Example part:** 6061-T6 cover ~150×100×12 mm, two M6 ports, one ground pad, outer cosmetic faces. With STEP + **TYPE II CLEAR; MASK GROUND PAD; PLUG M6; PAINT BLACK EXTERNAL ONLY; SEAL LAND — NO PAINT**, expect a usable finish planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with “anodize + paint black” and silent pads often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague paint RFQ versus a labeled mask/plug/paint pack and the clearer estimate path.
What widens bands fastest
Silent ground pads, unplugged fine threads, paint over seal lands, and laser-mark order left ambiguous. Quantity breaks help unit minutes but do not erase finish-map risk—see [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost) and [laser marking before vs after anodize](https://3dwk.com/resources/laser-marking-before-vs-after-anodize).
What to do next
Attach a mask/plug/paint-boundary note block, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Service pages: [CNC machining](https://3dwk.com/cnc-machining-service.php), [materials](https://3dwk.com/materials.php). Treat **rates.v1.1** min/mid/max as estimates, not invoices.
Common questions
Can “mask as needed” work?
No. Estimators need named faces and hole lists.
Does Type III change mask notes?
Yes—hardcoat thickness and edge build-up raise keep-out importance. State Type II vs III explicitly.
Should plugs be called out per thread?
Yes for production RFQs—list sizes or a hole table.
Is chem-film a substitute for mask notes?
No. Chem-film is a different finish path—see the chem-film vs Type II resource linked above; still name paint boundaries.