CRL Single Seal Insulating Glass Spacers have a proven record for utility and satisfaction over many years of use. Single Seal Spacers have a single shoulder to accept the sealant, and this shoulder is deep enough to allow for excellent sealant penetration. Insulating glass is the single most effective product that you can provide for your customers to save energy and cut heating and cooling costs. To prevent energy loss through glass areas, window manufacturers have turned to the production of insulating glass units. Private labeled spacer can be produced by imprinting your name on each spacer.