A mat is an important yoga prop and not just for standing on and marking your territory. It provides traction for hands and feet, padding for bones and is used in various ways for many poses. For example folded up on a chair for supported back bend, rolled up to support under the heels in squatting pose and folded up for headstand just to name a few.
Mats have various thickness and are made from different materials. For hard surfaces at home you may wish a thicker padded mat for knee and ankles relief but make sure it is not too bulky or thick that it does not have the versatility for other uses.
You may prefer a lighter, thinner rubber mat if you are transporting your mat to and from the studio. I prefer to fold my mat into a small square to put in my bag or backpack as opposed to rolling it up. One of the best mats for grip and versatility I have found are the Manduka Eko Light mats which have 2 thickness choices.(I prefer the thinner one for ease and versatility.) Giam Mat is also popular with long time students and has a spongy grip mat that is light with a little more padding.
Mats can be bought online if you search around on Yahooshop, Rakuten and Amazon for special deals or you can shop directly from yoga product companies many of which have branches in Japan. If you have a favorite mat let us know about it and why it is your favorite!