The Science of Blanketing is under valued.
Shielding from the cold, rain, sun or pesky no-see-ums and flies- consideration must be taken into account of the Horses' anatomy.
Understand that the Horse's ligament and muscle system needs to move under the weight of the blanket, ( this is why most blankets have a nylon liner) the shoulders must be free and the wither area contoured and respected. If you see a horse strapped in- it is not anatomically correct. The weight of the blanket causes constriction of the fascia and creates trigger points. By using the same blankets day in day out- you increase the contraction of the ligament and muscle system.
Please take measures to swap out blankets, using the turn out for turn out and stable for stabling- this will allow for the relaxation of the ligament and muscle system.
Please consider: NO DOUBLING UP BLANKETS as added lines of constriction are now formed by multiple layers.
Care and Maintenance of the Blanket is key.
For Cost Efficiency of manufacturing a product, the material is stretched for cutting. Once the material is washed- the flush of the wash cycle will swell the fibers of the material; the agitation of the spin cycle will "whip" out the fluid- and the fibers will to revert to their actual size- that is why items shrink- your blankets are no different. It is the Binding used around the material that will stabilize the shrink; yet, the Binding- which is synthetically treated, will bear the same result with multiple washes.
From the center to chest to the dock of tail is the standard of measurement. There are also considerations of height of withers, width of back, and height of horse. Horseware Ireland (shop.horseware.com) to have a varied selection to all shapes and sizes of the Horse; Schneiders (www.sstack.com) is one of my favorites as it offers the adjustable neck and belly bands. I prefer mid-neck verses standard neck as the mid neck will allow the cervical vertebra to offset the weight taken upon the wither area.
Straps and hardware are sewn on to ensure that they do not interfere with your horse's movement- running, jumping, twisting, rolling, you name it. Please make sure that leg straps are in good condition; any excessive stretch in the elastic is an accident waiting to happen. Rusty hardware must be replaced!