Most thermoses rely on double wall or even triple wall construction and the space between each wall is vacuum sealed.
													
																	Thermos vacuum insulated double wall. 
								
	
		
	
																	Note we don t call it the stainless jester. 
																	Hydrapeak 67oz water bottle double wall stainless steel vacuum insulated thermos canteen wide mouth flask bpa free leak proof growler with handle lid lilac 4 7 out of 5 stars 173 29 95 29. 
																	Thermos vacuum insulation technology for max temperature retention. 
																	How does a thermos work. 
															
													
								
	
		
	
																	Thanks to our industry defining double wall stainless steel construction the stainless king tumbler s vacuum insulation is as powerful as it gets. 
																	Vanfrost oe f 0035 double wall vacuum insulated stainless steel thermos wide mouth leak proof travel sport tumbler flask keep drinks cold 12 hours hot 24 hours 30 oz 3 8 out of 5 stars 79 18 99 18. 
																	Durable double wall stainless steel. 
																	Keep em cold for up to 18. 
															
													
								
	
		
	
																	Keep beverages hot for up to 7 hours. 
																	Air is effective at transferring heat.