In order of prefence:

Harlan teklad
Petsmart brand
Pecto brand

Depends on where I am when I need Aspen. Petco brand is shaved and the other 2 are shredded. The shredded works better for clumping/cleaning and making tunnels for snakes that burrow fully, the shaved is nice for the BPs/bigger snakes to cover themselves in when they want to burrow.