oil filter

I have a 94 Mustang gt convert and I am going to change the oil for the first time since i owned it. When I go to the store to get the filter I keep seeing two different filters... one that has a (d) and one that has a (t) I bought the (d) one which is the fram xg8a. not the xg16. Whats the difference? Any help would be great. :bang:
 
thanks everyone. I ended up putting the XG8A fram extended guard filter. It fit with no probs. Cleaned out the air filter too. What a PAIN IN THE A-hole. Talk about a crummy design. I'll definetly get a cold air intake next time. Thanks again.