Just changing my sump gasket and have just noticed that one of the new 'half moon' seals that I have are different to the ones that have come off the sump..

New ones on left and old on right:



Obviously the front seals are the same but the rear on the old one has the tab to sit up inside the block.
Are the new ones interchangeable front and rear or have they sent me two 'fronts' by mistake? What I'm getting at is do I need the one with tabs for the rear?

Why is nothing ever simple?
Cheers