Yoga bolsters can have a foam core, although not all of them do. As long as the bolster fulfills your needs, material other than foam is a feasible choice. Yoga bolsters need to give you additional support for challenging poses for which you need a boost and restorative poses in which your body needs to be resting rather than straining.
Foam Cores
Yoga bolsters with foam cores are the densest, heaviest and most supportive of the lot. The foam is generally synthetic, durable and firm. The foam can be the only insert inside the bolster, or the bolster can have a foam core wrapped with cotton batting to make the bolster softer.
Other Cores
Bolsters that don't have a foam core are usually packed with cotton batting or chambray, a lightweight, all-natural material. Bolsters lacking foam can be just as heavy and supportive as their foam counterparts long as the batting is densely packed. The batting can be packed directly inside the bolster's zippered covered, which gives you the option of removing a portion of it to adjust the bolster's height for your individual needs. Smaller supports, such as neck pillows or yoga cushions, usually contain cotton batting or buckwheat hulls for filler.
Foam Vs. Other Materials
Foam cores are a single solid block, which means you can't adjust the bolster's height. Because they are solid, the foam has less of a chance of shifting or depressing from repeated use. Because the bolster's outer covering is usually cotton, bolsters filled with cotton and chambray give the bolster the claim to fame of being 100 percent natural or even 100 percent organic.
Buying
Yoga bolsters are available at retailers that specialize in yoga accessories and props as well as stores that sell a variety of mats and pillows. The cotton-only bolsters were the least expensive, priced at $38 each for a 10-inch round, 28-inch long bolster, as of in February 2011. Bolsters with a foam core wrapped in cotton were priced at $43 each for a 9-inch round, 27-inch long bolster. The 100 percent organic chambray-filled bolsters were the most expensive, priced at $90 for a 9-inch round, 27-inch bolster.
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