When I was first learning the Magic Loop Method I heard about KnitPicks and Addis as the only two companies that produced long flexible cables. The needles need to be 100 cm or 40 inches in length for most projects. Since I was purchasing them for socks, I bought the Options (metal) fixed circulars in US size 0 or 2.00 mm, US size 1 or 2.5mm. I also purchased the Harmony (wooden) fixed circulars in US size 2 or 2.75mm and US size 3 or 3.25mm. They were okay. The wooden ones have very sharp points and the yarn wouldn't slip well off the needles. I was constantly pushing the yarn off with my index finger. After a short time, the tip of my index finger was sore which limited my knitting time. KnitPicks does not offer fixed circulars from sizes US 4 to 11 or 3.5mm to 8mm. I didn't want interchangeables at the time because I was concerned about the joins.
I was looking for some very small needles sizes 000000 (6-0) or 0.7mm to 00 or 1.75mm because I wanted to knit socks and I knew that I knit loosely. The only company that I found that carried those sizes in the fixed longer flexible cables was HiyaHiya. I bought sizes US 4 or 3.5mm, 5 or 3.75mm and 6 or 4.0mm in the 40 inch or 100 cm length just to see if I liked them.
I fell in love with the needles. The needles are made of stainless steel and the yarn glided off the needles with ease. I didn't have to push the yarn off with my index finger. I now have the smaller interchangeable set which goes form size US 2 or 2.75mm to US 8 or 5.0mm. I use them exclusively now. They come cables in four lengths that make the total length of the circular needles 1) 16 to 18 inches or 40cm to 46cm, 2) 24 to 26 inches or 60cm to 66 cm, 3) 32 to 34 inches or 80cm to 86 cm and 4) 40 to 42 inches or 100 to 106 cm. They also have an additional cable that can be purchased which makes the circular needles 152 cm to 158 cm.
The reason for the difference in length is that they come in 4 in (10 cm) or 5 in (10.3 cm) tips. I chose the longer tips.
The HiyaHiya needles are great.