A cable described only as “6 mm² flexible copper” leaves key purchasing decisions unresolved. It does not identify the conductor construction, prove terminal acceptance, show that the finished cable fits the gland, or establish its bend radius.
Treat those as four connected but separate evidence checks. Record the conductor identity, match it to the exact termination, compare the finished outside diameter with the gland range, and verify the finished cable's routing duty. This guide provides an RFQ structure; it does not reproduce paid standard tables or assign universal strand, resistance, pull-force or bend-life limits.
Start with conductor identity, not nominal area alone
Record the material and plating, nominal area, declared construction or class, standard and edition, and offered cable part number. Identify the reference temperature and acceptance source for any resistance report.
The public scope for IEC 60228:2023 says the current fourth edition covers nominal cross-sectional areas from 0.5 mm² to 3,500 mm², requirements for wire numbers and sizes, and resistance values. It includes solid, stranded and Milliken conductors as well as flexible copper conductors, and generally addresses conductors in finished cables. The public page does not expose the normative class tables or their numerical limits, so an RFQ should request a declaration and applicable report rather than recreate those tables. IEC 60228:2023 public scope.
Do not replace a declared construction with the word “flexible.” The LAPP ÖLFLEX SOLAR XLS-R data sheet for article 0023138, dated August 20, 2026, identifies IEC 60228 Class 5, fine-wire. A separate LAPP ÖLFLEX AUTO 8681 MC specification, document HDB85189001EN revised November 17, 2023, identifies Class 6 and gives its own moving and fixed bend data. These are named examples, not proof that every cable in either class has the same routing capability. LAPP Class 5 cable specification and LAPP Class 6 cable specification.
If a supplier offers an alternative conductor construction, ask for the revised data sheet and an interface review. Equal nominal area does not by itself establish equal finished diameter, terminal preparation, resistance evidence or movement performance.
Match the exact conductor form to the exact terminal
Give the bidder the terminal block, contact or lug manufacturer and complete part number. Request its accepted conductor forms and size ranges, stripping length, need for a ferrule or other preparation, and the specified torque or application tooling. Keep these data tied to a document revision.
IEC 60947-7-1:2025 is the current fourth edition for industrial terminal blocks with screw or screwless clamping units. Its public scope covers round copper conductors, with or without special preparation, over its stated range and up to 1,500 V DC. That broad scope does not say that every terminal accepts every conductor form within the headline range. IEC 60947-7-1:2025 public scope.
A Phoenix Contact protective-conductor terminal provides a useful product-specific illustration. Its US 6-PE page identifies IEC 60947-7-2 and lists a rigid-conductor range of 0.2–10 mm², a flexible range of 0.2–6 mm², and flexible conductors with ferrules from 0.25–6 mm². It also lists an 8–10 mm stripping length and a tightening-torque range. These values apply to that exact terminal and product standard; their value here is to show why a sales description such as “accepts 10 mm²” is incomplete. Phoenix Contact US 6-PE product data.
For crimp contacts, treat wire, barrel and tooling as one controlled connection. IEC 60352-2:2024 publicly describes solderless crimped connections using appropriately designed barrels and specified wire forms, and it addresses suitability under mechanical, electrical and atmospheric conditions. It also notes comparison of results made with tools of different designs. The purchased standard and the contact manufacturer's instructions govern the actual requirements. IEC 60352-2:2024 public scope.
Use the wire-ferrule and terminal compatibility guide when a ferrule is part of the proposed preparation. Do not add a ferrule by habit or omit one by assumption; require the preparation approved for the exact terminal and conductor.
Select the gland from finished cable geometry
A conductor class is not a gland size. Request the finished cable's nominal outside diameter and tolerance, shape, jacket material where relevant, and the condition in which it enters the enclosure. Then name the gland part number, thread, entry interface, published clamping range, sealing parts and strain-relief function.
IEC 62444:2010 remains the published cable-gland standard with a 2028 stability date. Its public scope addresses construction and performance requirements and tests for complete glands as supplied. The public summary does not provide a rule that converts conductor class or mm² into gland size. IEC 62444:2010 public scope.
Manufacturer data normally makes the geometry visible. As one named example, LAPP describes SKINTOP CLEAN article 53110020, an M12 gland, as sealing and strain-relieving a cable entry and publishes a 4.5–6 mm clamping range. That number is not a general M12 range. It demonstrates the correct RFQ comparison: the full cable-OD tolerance against the exact gland's published range. LAPP SKINTOP CLEAN M12 product page.
Check the thread and enclosure entry separately from cable clamping. A cable can fit the sealing range while the thread, panel thickness, locknut, washer or enclosure interface remains wrong. The cable-gland diameter, sealing-range and thread guide develops that interface review.
Keep conductor class separate from routing duty
Conductor construction contributes to flexibility, but it does not certify the performance of insulation, fillers, shield, jacket and overall cable under motion. Define whether the installation is fixed, occasionally moved, repeatedly flexed or torsional. Request the finished cable's applicable minimum bend radius, temperature range and movement restrictions from its own data sheet.
For repeated motion, state the travel, speed, acceleration, cycle expectation and torsion where the equipment designer requires them. A class label alone is not evidence of chain suitability or service life. A cable maker's product-specific moving radius or application statement is useful only for the named construction and documented operating conditions.
Use the strain-relief and bend-radius guide to define static routing and repeated movement. Avoid turning a typical bend-radius multiple into a universal acceptance value.
Return one compatibility matrix with every quotation
Give every bidder the same interface sheet. Require source documents rather than a simple “compatible” answer.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| RFQ line item | Evidence the bidder should return | Buyer hold condition |
|---|---|---|
| Conductor identity | Cable part, material/plating, nominal area, declared standard edition and class, applicable resistance record | Identity or document revision is missing |
| Terminal interface | Exact terminal/contact part, accepted conductor form and range, strip length, preparation and torque or tool data | Offered conductor does not appear in the exact terminal data |
| Gland interface | Finished cable OD with tolerance, gland part, thread, clamping range and sealing/strain-relief data | Full OD tolerance or entry geometry is not covered |
| Routing duty | Finished-cable bend data and relevant motion/environment limits | Supplier evidence covers a different duty or cable construction |
| Production control | Work instruction, controlled tool or torque record, first-article dimensions and agreed tests | Evidence cannot be traced to the quoted revisions |
Do not ask for certification against an unnamed “industry standard.” State the governing product and installation requirements. If the project needs a pull, resistance, ingress or movement evaluation, define its method, sample basis and decision rule through the applicable specification.
Review an invented quotation example
The following comparison is fictional and is not a supplier result, product recommendation or SINAWATTS capability claim. Quote A says “Class 6, 10 mm², M20 gland” but supplies no cable part number or OD tolerance. Its terminal sheet lists only a headline clamping capacity, and its bend claim has no data-sheet reference. Hold the quote: three interfaces remain unverified.
Quote B names the cable revision and class, exact terminal range and preparation, cable OD tolerance and gland range, and finished-cable bend limit. It is reviewable, although fuller evidence does not guarantee acceptance.
Close the RFQ with traceable deliverables
Request the cable, terminal and gland data sheets with revision dates; an assembly drawing; preparation and tooling instructions; and the agreed first-article record. Ask the supplier to list assumptions, deviations and substitutions. A later change to conductor construction, terminal, preparation, cable OD or gland should trigger the defined review authority even if the commercial assembly number stays the same.
Send the declared conductor class and size, material, terminal and gland part numbers, finished cable OD tolerance, routing duty and required evidence with the enquiry. Ask the bidder to return a document-linked compatibility matrix before acceptance.
Send a cable-interface evidence RFQ
Buyer FAQ
Is nominal mm² enough to select a terminal?
No. Verify the exact conductor form, size and preparation against the exact terminal or contact documentation. Manufacturer data can give different ranges for rigid, flexible and ferruled conductors even when one headline maximum is advertised.
Does a Class 6 conductor automatically fit a flexible-wire terminal or cable gland?
No. Terminal acceptance comes from the terminal manufacturer's documented conductor range and preparation. Gland fit comes from the finished cable outside diameter and the selected gland's published range. A class designation proves neither interface by itself.
Do fine-stranded conductors always require ferrules?
There is no safe universal answer in the public standard summaries. Follow the exact terminal manufacturer's approved preparation and the applicable equipment or installation requirements. State that preparation in the drawing and RFQ.
What should accompany a first-article cable assembly?
Request documents tied to the exact cable, terminal and gland revisions: construction data, interface data sheets, preparation and tooling records, controlled dimensions and any electrical, mechanical or ingress evidence explicitly required by the drawing or purchase specification.