These are ideal for storing rare pamphlets, magazines, folded maps or other items which are up to 1/4 in. thick. They feature .040 board backs and .004 polyester L-seals held in place using archival polyester-based tape. The L-seals offer the advantage of easy insertion, with the opening facing toward the spine of the binder for secure storage. Polyester L-seals offer two further advantages over traditional binders with archival paper envelopes mounted inside. In the first place, crystal-clear polyester allows immediate visual recognition of the item inside; furthermore, unlike envelopes with flaps and center seams, the L-seal places no pressure points against the material stored within it. Select either .040 Lig-free I or .045 MicroChamber backing board by indicating the appropriate item number from the list below. Bear in mind that items should be somewhat smaller than the insert size indicated below to accommodate the thickness of the item while allowing the binder to close completely.