Cheapest sound grenade at this time
The product is working with normal airsoft gases and use a paper choke. The gas make pressure on paper and after mechanical shock, there is a ball bearing which hit the paper and release all the gases. The gas make noise which aroung 70dBi loud. A ThunderB is much louder and more expensive to use. This grenade can use "empty gas can" as power source which can be used for GBBs or GBBRs so now I have my many "empty cans" a real purpose of use.
This item is nicely machined from aluminium. It is very long-lasting and it can be used with 5 sheets of A4 paper also. Easy to refill with gas and easy to rearm/reload. One use is around 0,2-0,3€ cost which is 4times cheaper as a ThunderB.
Be carefull, don't forget to relube the loading tube which often completely dry and cause wokring problems!