318ti Rear Blade Refill - part# 61621381754 ------------------------$7.62
318ti Front Blade Refill
up to 03/96 part# 61611372747(x2)----$4.40
318ti Front Blade Refill
after 03/96 part# 61618220913(x2)----$9.39
*note---> this is according to realoem, I'd check and make sure that your blades aren't different lengths since realoem has them listed as the same part# for both sides.
**Also note that according to realoem, the 1990 325i convertible uses the same blade refill as the 318ti, part# 61611372747(x2)----$4.40
***Again, these were the prices listed on Tischer's website.
Here's the links to the realoem diagrams:
318ti front wipers
http://www.realoem.com/bmw/showparts...69&hg=61&fg=45 318ti rear wiper
http://www.realoem.com/bmw/showparts...99&hg=61&fg=45 '90 325ic wipers
http://www.realoem.com/bmw/showparts...56&hg=61&fg=45