11-87 will handle 2.75" and 3" in the same gun. Most 1100's were designed for 2.75" shells only. They did make some 1100 Magnums that would handle 3" shells and heavy loads of 2.75". The 1100 Magnums will not reliably cycle light 2.75" loads.
The new 1100's will handle 3" shells. They came back out with the 1100 after years of absence at the request of customers. I have no experience with the new ones though.