groucho::: Aside from sir edzzz's sound advice, here's my 0.002 :D

1. To determine the excact wiper blade length, you simply take a ruler or measuring tape and get the exact length of the rubers from tip to tip. From there, you will just have to tell any accessory shop your required blade length. Don't worry about the clips and locks, they should be included with the set. Newer models are sold with uneven woper blades. But some models still use same length blades for older units, more on SUVs.

If you have the extra effort and time, run your washer a couple of time to see if your windshield can still accomodate longer blades. About half an inch on top and bottom parts should increase your overall length by an inch.

2. Aftermarket wiper blades can be bought in singles. Some accessories shops in Banawe sell them by piece. But it will not cost 50% of its boxed price. More like 75% of the kit.