Per Briggs and Stratton 
698717 GASKET-CYL HD
Part Superseded From: 272170
Alternate Parts: 4123 Package of 5 Each
The 698717 also replaces 
Briggs and Stratton 	270341
Briggs and Stratton 	272536
Briggs and Stratton 	272536S
I too am wondering why the change up. I would need to order in the 698717 on my next stock to verify the shape change and material used as I got about 5 of the older metal version on hand.