vacuum flask 1)double walls 2)12 hours keeping warm 3)1.0L-4.0L vacuum flask12hours keeping warmdouble wallsplastic part:brand new plastic VC-12B,VC-15B,VC-20B,VC-25BAvailable size:1.2L,1.5L,2.0L VC-30BAvailable size:1.0L,1.3L,1.6L,1.9L AVC-35BAvailable size:2.5L,3.0L,3.5L,4.0L