The Jeep JK grille has 4 sizes. Looking at grill from left to right number them 1 to 7. One and Seven the two outer holes, with four being the center hole. The last 3 number on the file name are the designs length in millimeter. I printed mine in ABS. Had them in about 500 miles and still seem to be good.
1 & 7 use file ending in _273
2 & 6 use file ending in _275
3 & 5 use file ending in _277
4 (center) uses file ending in _278