These reusable cups have several advantages over glass cups and jars for rooting cuttings in water. Their opaque walls block direct sunlight, slowing evaporation so the cup won't dry out quickly, and the dark environment also protects the sensitive new roots from UV rays and discourages algae growth in the water.
The funnel-shaped cap holds leaves above the water, and has a slit that lets you take the stem out from the side, avoiding damage to the roots. Made from tough, flexible silicone, the cups won't break if dropped, and can be cleaned in a dishwasher or sterilized in boiling water.
The small cup is a good size for individual cuttings of flowers and herbs, and the large cup is excellent for forcing bulbs or for large cuttings. Small cups are available in green or dark gray, large cups only in green.