One thing first:
Yes, it stays tight.
The delivery took place within 7 working days from the UK.
First I tried the housing pool. (Of course, without a camera)
Then we went to almost 20 feet in salt water.
Here you already feel like the O-ring operates (it has slightly geknarzt).
But here everything has remained dry.
After these initial tests, I spent 13 wonderful days diving with excellent results.
Also, the housing offers enough space to accommodate silicate bag.
A thread for an external flash arm and optical connections for the lightning is present.
CONCLUSION:
Strong buy recommendation and qualitatively no different from the expensive Canon original.