3M™ Dual Lock™ Reclosable Fastener SJ3811, Pop-in Piece Part, StemDensity 400, Black, 26 mm x 26 mm, 500 Piece/Case

3M Dual Lock Reclosable Fastener SJ3811 is a black, polypropylene reclosable fastener with a pop-in square top, a rectangular base, and a stem density of 400 stems per square inch. This fastener is designed to overcome the alignment and installation problems of screws and hidden fasteners. It offers simple installation with no special tools required. The fastener attaches without the use of pressure-sensitive adhesive and comes with a variety of bases that can be inserted into holes of precise dimension. It is easy to install and requires no special equipment or skills.

The 3M Dual Lock Reclosable Fasteners are positive-locking, blind fasteners specifically designed for attaching automotive trim components. These fasteners feature mushroom-shaped polyolefin stems that snap together, forming a high tensile closure. They are primarily used to secure rigid and semi-rigid surfaces such as trim or door panels, instrument panel bezels, headliners, and other automotive interior and exterior trim.

How It Works
This pop-in fastener is designed to be popped into a slot or hole where attachment is desired. The polypropylene disk base grips the inside of the hole and holds tight. The fastener can then be mated and engaged to a second Dual Lock fastener attached to a piece of trim or other part. When closed, the two parts firmly secure together.

When two pieces of 3M Dual Lock Reclosable Fasteners are pressed together, the stems flex and the mushroom heads slide past each other. After passing the opposing mating piece, the stems snap back into their original position and the opposing mushroom heads interlock. These fasteners provide high tensile strength but can be opened by simply cleaving or peeling open the closure. Alignment and re-alignment are easy, and no special tools are required for installation. This means that they can be used to attach components before they enter the final assembly plant, helping to reduce the number of parts and assembly time.

Stem Densities
Combinations of stem densities and the engaged area provide adjustable and proportional engagement and disengagement force to meet the needs of the application. Dual Lock fasteners are offered in three different densities (stems per square inch): 170, 250, and 400. The Dual Lock fastener SJ3811 has 400 stems per square inch, offering the tightest hold, and can be mated to Type 170 or 250. It should not be mated with another Type 400 fastener because the hold would be so tight that detachment would likely result in damage to the parts.

Applications
3M Dual Lock Reclosable Fasteners can replace conventional mechanical fasteners in a wide range of assembly and attachment applications where reclosability or serviceability is desired. They are used primarily to secure rigid and semi-rigid surfaces such as trim or door panels, instrument panel bezels, headliners, and other automotive interior and exterior trim. Some examples of applications include:

• Vehicle headliners
• Attaching accessories and equipment
• Attaching window and door trim panels
• Vibration and sound damping control
• CHMSL cover plates
• Center console flanges
• Interior trim
• Sunroof rings