< 3M Dual Lock reclosable fastener with acrylic backing >

Dual Lock Reclosable Fastener

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Dual Lock 400 Reclosable Fastener (SJ3551) - One Strip: 1" by 1 ft 



Dual Lock is the strongest fastener system on the market, and this is the strongest version of Dual Lock (400 pins per square inch). Unlike Velcro, there is no "hook" or "loop". Each strip is open on one side and able to be fastened to any other strip. Dual Lock has up to 5x the tensile strength of typical hoop-and-loop products and is the only reclosable fastener strong enough to allow you to install mass loaded vinyl in your vehicle. 


Product Instructions

  • Mushroom shaped stems interlock with one another when pressed together, creating a fastener much stronger than industrial strength Velcro. 
  • Super strong, pressure sensitive acrylic backing will stick to metal, wood, vinyl, cardboard, glass, concrete and most plastics. Will not adhere to fabrics or rubber. 
  • Application surface must be clean, dry, and free from oil.
  • As a general rule, 4 square inches of fastening area are required per pound of static load. More Dual Lock coverage is needed for high temperature or high vibration use cases.
  • For maximum bond strength, apply at room temperature and allow 24-48 hours before fastening. If you try and fasten/unfasten right away, the Dual Lock will be stronger than the adhesive backing.
  • You can further improve resistance to edge peel by recessing the fastener or rounding the corners.
  • Dual Lock should only be used inside the vehicle. Do not apply in the engine compartment or exhaust tunnel.


Product Specs

  • 400 pins per square inch. Able to mate with the 170 and 250 versions. A higher combined number means greater closure strength.
  • Each strip is 1" wide by 1 foot long. The fastener must be applied to both the application surface and the material you are applying.
  • 25mm thick with an acrylic self-adhesive backing
  • 1000+ closures
  • Service temperature: -20 to 158 F (intermittent to 200 F)
  • Resists hot/cold cycles and water


To get the most bang for your buck, Dual Lock strips should be cut somewhere between 1" x 1" squares to 1" x 6" rectangles depending on the weight of the material being fastened. One strip is 12" long, and can be cut into two 1" x 6" pieces for a total of 6 square inches of coverage. For a rough estimate of the total amount of Dual Lock needed per sheet of Second Skin mass loaded vinyl or foam, see below:



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