Spiral Duct and Fittings

MKT products are factory fabricated to meet or exceed 3rd edition 2005 SMACNA Standards. MKT standardizes most spiral duct with USA mill-stamped, G90 galvanized steel*. We not only meet requirements set by the state and federal entities, but our highest standards are held by our own quality control guidelines. 


Customers are able to purchase spiral accessories from MKT as well. In addition to the 10′ lengths, MKT inventories elbows, air-tites, high efficiency take offs, bell-mouths, duct connecting systems and duct hanging systems.

Materials used in the production of spiral duct:

  • Galvanized
  • Galvaneal or “paint grip”
  • Aluminum
  • Stainless Steel
  • PCD coated
  • Powder coated
  • Agion® Antimicrobial

Diameters produced: 3″ to 100″ capabilities

Lengths produced: MKT produces and inventories 10-foot lengths of all diameter duct. Specific lengths, longer or shorter than 10 foot are available, up to 20-foot maximum.

Gauges: 18 to 26

Double wall insulated duct:

  • Perforated inner wall for insulation and decibel applications
  • Solid inner wall for insulation only

Connection Types


  • Self Sealing w/ rolling O-ring gasket
  • Time and labor saving
  • Easily adjustable without damaging the flange
  • Laboratory tested to be in accordance with UL 723 and NFPA 255 standards



  • MKT recommends using slip in couplings up to 24″ diameters
  • Quick, simple, relatively inexpensive
  • Light to moderate strength characteristics
  • Requires sealing in the field if necessary



  • Simple installation process
  • Can be installed on-site
  • Shop installation has proven to protect the ends of spiral in transit and reduce labor time in the field
  • Available in 8″ to 72″ in standard 2″ increments
  • Requires sealing in the field or the shop if necessary

Barrel Clamp


  • Self Sealing
  • Time and labor saving
  • Adjusts automatically to slight duct diameter variations
  • Has been lab tested to 18″ positive WG and 10″ negative WG

Angle Rings


  • Typically used in heavy, industrial applications
  • Larger diameter and gauge spiral/round duct uses angle rings
  • Can be used in conjunction with “van stoning” on the round duct for a “slip ring” capability
  • Requires additional gasketing if required
  • Available in all materials including galvanized, pricing and availability on request