This set of high-quality, durable plastic bottles helps to illustrate and reinforce concepts of volume, mass and capacity.  The set includes four different sized, sealable bottles: 2 litre, 1 litre, 500 ml and 250 ml.  Each bottle has markings in both metric and imperial scales, as well as different coloured caps.  The set comes with an activity booklet and conversion tables in four languages (English, Spanish, French, and German), and the bottles are heavy-duty and washable for years of use (we recommend hand-washing).