The filter is on the outside Robo. Apparently they call it a side injector I think. I don't have a photo but this link is the same... http://gzhaoxiang.en.alibaba.com/pro...10_JS23_1.html

The filter is on the outside between the black sections.... so to speak.. Once you see the pic it'll make sense.. Let me know if the link doesn't work. Basically I just googled JS23-1 and its the first link.

Cheers Rob..