1. This is a triple Needle used for domestic sewing machines you would use this needle if you wanted to use 3 threads at the one time. They could be in different colours

When using a triple needle, straight stitch, Stitch Length never over 2, width 0 . Always check by turning the fly wheel of your machine. that the needle is not going to hit the sewing foot of your machine as it will instantly BREAK

Fit these machine needles into the machine with the flat side to the back

TIP:

Always have a spare needle available as you may break your triple needle