Felting needles are barbed needles that can be used to interlock wool fibers. As the needle is moved up and down, the barbs catch the scales of the wool and entangle them, creating felt.
 
This pack of three felting needles are blue 36,  pink 38, &  yellow 40 -gauge triangular needles. The 36 gauge triangular needle is for fast coarse felting.  The 38 gauge triangular  needle is for medium finish felting leaves a smaller hole in the felted surface. It felts more slower than 36 gauge needle.  The size 40 is for finishing and fine detail leaving the smallest holes.
 
I hardly ever use a 36. 
 
you can can choose to order each in bulk