Lids are made of high density polymer foam. They are a lose fit in the flask to allow gas venting. They will not contain a spill

insulating stopper
Insulating Lids for Cylindrical Dewar Flasks  
SKU DESCRIPTION For Flask For Flask PRICE    
KGW-1721 Insulating Lids for Dewar Containerfor flasks KGW-1021 KGW-1021 $23.00
KGW-1722 Insulating Lids for Dewar Container for flasks KGW-1022 and flasks KGW-1061 KGW-1022 KGW-1061 $23.00
KGW-1723 Insulating Lids for Dewar Container for flasks KGW-1023 and flasks KGW-1062 KGW-1023 KGW-1062 $23.00
KGW-1724 Insulating Lids for Dewar Container for flasks KGW-1024 and flasks KGW-1063 KGW-1024 KGW-1063 $23.00
KGW-1725 Insulating Lids for Dewar Container for flasks KGW-1025 and flasks KGW-1064 KGW-1025 KGW-1064 $23.00
KGW-1726 Insulating Lids for Dewar Container for flasks KGW-1026 and flasks KGW-1065 KGW-1026 KGW-1065 $23.00
KGW-1727 Insulating Lids for Dewar Container for flasks KGW-1027 KGW-1027 $23.00
KGW-1728 Insulating Lids for Dewar Container for flasks KGW-1028 and flasks KGW-1066 KGW-1028 KGW-1066 $23.00
KGW-1729 Insulating Lids for Dewar Container for flasks KGW-1029 and flasks KGW-1067 KGW-1029 KGW-1067 $23.00
KGW-17210 Insulating Lids for Dewar Container for flasks KGW-10210 KGW-10210 $23.00