The offset would make a difference if you plan on putting this on a Chrysler 300 RWD. Because those wheels won't work. If you are looking for a 18" wheel, try one that is 18x8 and with an offset of approx. 15-25mm.
17X7 5-115 Offset 38
18X7.5 5-115 Offset 38
Does the offset make a big diffrence?
What is the correct Offset for the 17" & 18" rims?