I've used this guide and it worked out well for determining the size of the transmission line, it should help determine which filter you need.
If the flare nut takes a 1/2" wrench then your line size is 5/16".
If the flare nut takes a 5/8" wrench then your line size is 3/8".
If the flare nut takes a 3/4" wrench then your line size is 1/2"
As already mentioned make sure you have the right size before you cut anything.
If the flare nut takes a 1/2" wrench then your line size is 5/16".
If the flare nut takes a 5/8" wrench then your line size is 3/8".
If the flare nut takes a 3/4" wrench then your line size is 1/2"
As already mentioned make sure you have the right size before you cut anything.