...something other reviewers seem to have missed is that in this particular product the bag of sand allows you to hatch many generations of Triops
Once your first batch have reached adult stage (about 2 weeks) the majority of which will be hermaphrodites that lay fertilised eggs in the sand.
After they all die you can let the tank dry out for a month or so and then a re-filling of the same type of water used should see a whole new bunch of hatchlings.
'Triop World' is one of the few kits to mention this in the instruction booklet AND provide the sand. Some other kits on the market include gravel - but I have found sand works better for getting the Triops to lay eggs in.
This makes it especially useful as an educational tool because children can see the cycle of life right before their eyes.
The only thing left out of this kit which would give it a 5 star rating is the lack of a mini strip thermometer. That would enable you to make sure the temperature is correctly maintained for the first few days - which is crucial in successful hatching of the little creatures!