Vintage Mid Century Spill Resistant Drinking Cups By Mathew J Kramer & Jet X Co. Denver Colorado , A little history about Mathew J Kramer & The Jet X Co, The cups was designed to be a spill resistant drinking cups with sliding internal partitions, patented by Mathew J Kramer in the 1950s and then later by the Jet X Co, possibly in the 60s and early 70s both are located in Denver Colorado, about condition of the cups, they are in great condition with multicolored cups and sliding partition, They measure 3 1/2 inches in height with the mouth of cup being about 3 inches around, the base measures about 2 1/2 inches in width, the sliding partitions measure 3 1/2 at the widest point and 2 3/4 inches at it’s smallest point 3 inches in height, the plastic itself may be a polyethylene, cups weighing about 2 1/2 to 3 oz each there are 5 jet x cups and one Kramer cup