It's Aspen.

I have a question or two.... Alot of people talk about impaction. With leopard geckos I hear loads about impaction caused by sand. Now, do snakes actually eat bark and stuff when you have it as substrate? I much rather have used bark, it looks much better. Instead I used aspen just because I've heard better things about it.

Is bark really that bad? I've seen a few tanks with bark, and if its ok, I'd like to switch it with my aspen when I need a big cleaning.