These straws are great. Kids can easily blow bubbles, but it is impossible to suck up liquid through the straw - exactly as advertised.
I used them with middle school students for a science experiment about Carbon Dioxide - they blew bubbles into a CO2 indicator solution, and the one-way straws made sure nobody accidentally (or on purpose...erg middle schoolers) swallowed the indicator solution. Perfect.
(Plus, the plastic one-way filter in the bottom of the straw can be popped out (by an adult, it takes a bit of effort) and fitted into any bendy straw for infinite re-use.)