My new inlet valve is different

[Siena911]

The guys doing the heads on my car have let me know that I need to get one inlet valve.

I have ordered the part and it arrived, but I have a question about it. It looks like the ribs that the "collett" or valve retainer etc clamps against is slightly different.

I have attached a picture of the two valves. The one on the left is the new one and the little ribs are slightly narrower. When it is all assembled with the retainer and the springs pushing against it, surely this won't move anywhere?

Is this safe to use? The opinion of the parts supplier is that they have never had one of these returned due to failure etc.

Any one else come across this?

Any feedback appreciated.

Regards,
Jakes