These Archival CLAMSHELL Original Comic Art Storage Boxes come in either 11 x 17" or 13 x 19". They also come in Blue-Gray or Black Barrier Board. The material is acid-free, lignin-free and comes with a 3% calcium buffer which prevents migrating acids from entering the box. These boxes have passed the P.A.T. test which certifies them as being safe for Indefinite Storage.