Before the now defunct Fram Champ alliance known as Fram Filtration the S2808 was not an ecore. It was a Champ made classic construction filter with clicker type bypass. During the ff period that application became a Fram fiber endcap filter, similar to the 9688/3593a. Local AZs here still carry the former FF filter made STP line and that application hasn't changed from Fram construction. The STP S3614 is an ecore, and the 6607 classic Champ metal endcap construction.
In some other parts of the country the STP blue filters are now made by M&H Purolator.