Sewing machine needles by Schmetz are wellknown and of excellent quality.
Naaldsysteem: 130/705 HS-ZWI

With a twinneedle you can create professional looking seams in stretch fabrics without using a coverlock machine..
Sew two exactly parallel lines op top of your seam, the bobbin thread makes a zigzag that makes the seam stretch. 
Because of the medium ball point  the threads are softly pushed aside without damage. The shank and special scarf area prevent the machine form loosing stitches even in very stretchy fabrics.
With a twin needle you can make a seam in stretch fabric without loosing the stretch.
On the right side of the fabric you get the double stitchline and on the inside a zigzagstitch which makes the seam stretchy.

There are different widths available, please choose the desired with when ordering.
The wider twin needles can have the issue that sometimes a little hill forms between the stitchlines. This is easily prevented by using Solufleece tape on the bottom and top of your hem. It's soluable in water. So just sew and rinse away

Stretchtwin needles can be used on normal houdehold machines with a zigzag function. Place the needle inthde machine with the flat side away from you. Make sure that the sewing foot and needle plate have enough room to accomodate the twinneedle.

Tip: Use the twin mode button or something similar if your machine has that function to prevent the needle accidently hitting the needle plate and breaking.

You will need two spools of thread. If you don't have two spools just use a bobbon and place it under the spool on the machine. Make sure that the thread of the bobbin and spool unwind in the same direction.

For a decorative effect you can choose two different threadcolors!

Threading the needle: Take the two threads and thread them throught the machine as if the are one. When you get too the needle seperate them and thread them each through the eyes. There are machines with special seperating tools, if your machine does please follow the special threading instructions of your machine .

Please note that the automatic needle threader does not work when using twin needles! There are seperate needle threader available for sewing machines, coverlocks and overlocking machines: Needle threaders
 
Is chossing difiicult?
In this PDF we have made a manual for choosing fabric in combination with thread and needles: (dutch)
Garen en naalden gebruikstabel
TIP: a needle has a working lifespan of about 8 hours.

This does not mean you have to change your needles every day. It's like this: when you press the pedal of your machine down and hold it for eight hours straight. At the end of the 8 hours your needle needs to be replaced.

The easiest way of remembering to change your needles is to get a new one for every project.