Products for children. Consideration of toxic materials when the children put it in his mouth a bite or suck! The designer must consider the safety of the user is important. There are some design to use a technique called plain.Such as the spiral valve, gas cylinder head design, or the spiral lock blade of the fan. There will be open to the optimized patching opposite spiral spiral of general, for safety, for those who do not know or acquainted to rotate the is, the more spin the tightening.
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