Really really extra warm haramaki Merino Wool (with lycra for stretch)   

Super soft and cosy. Great for lower back pain. Very stretchy. Please note: not fluffy like the Angora haramaki. 

Size information here. If in doubt size down. 

Simple stretchy-knitted rib tube. Unisex. Kidney-warmer/Back-warmer. 

Fibre content: Merino with lycra

Machine wash but on wool wash cycle. Keep spin short then gently pull back into shape whilst drying. Air dry.

"Merino wool is common in high-end, performance athletic wear. Typically meant for use in running, hiking, skiing, mountain climbing, cycling, and in other types of outdoor aerobic exercise, these clothes command a premium over synthetic fabrics.

Several properties contribute to merino's popularity for exercise clothing, compared to wool in general and to other types of fabric:

•          Merino is excellent at regulating body temperature, especially when worn against the skin. The wool provides some warmth, without overheating the wearer. It draws moisture (sweat) away from the skin, a phenomenon known as wicking.The fabric is slightly moisture repellent (keratin fibers are hydrophobic at one end and hydrophilic at the other), allowing the user to avoid the feeling of wetness.
•          Like cotton, wool absorbs water (up to 1/3 its weight), but, unlike cotton, wool retains warmth when wet,  thus helping wearers avoid hypothermia after strenuous workouts (climbs) or weather events.
•          Like most wools, merino contains lanolin, which has antibacterial properties.
•          Merino is one of the softest types of wool available, due to finer fibers and smaller scales.
•          Merino has an excellent warmth-to-weight ratio compared to other wools, in part because the smaller fibers have microscopic cortices of dead air, trapping body heat similar to the way a sleeping bag warms its occupant."