How do you improve accuarcy without using moves?

Question

What hold-item is best to increase accuracy?
and how much does it boost it by? (in Diamond)

Answer 1

If your Pokemon are slow, use a Zoom Lens
If your Pokemon are fast, Wide Lens is the way to go.

Zoom Lens boost Accuracy By 20%

http://serebii.net/itemdex/zoomlens.shtml

Wide Lens Boost Accuracy by 10%

http://serebii.net/itemdex/widelens.shtml

Comments

Are they increased by that amount or increased BY?
So for example:
For Zoom Lens, lf l have a Pokemon that is holding Zoom Lens,
and uses Zap Cannon (50% accuracy) will it be increased to:
50+20 = 70%  
or  
50+50x0.2 = 60%?

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50+.2=60 is correct MidnightSky