The B+W Push-On Lens Cap #300 model is their 'standard' unit, and has a slightly convex front surface to prevent the inside of the cap from touching the glass of your lens when it is tucked away in a bag. The sides are their 'standard' depth, to fit on normal lens barrels or standard-style filters, and this particular unit has a 32mm inner diameter.
B+W also makes a 'shallow' sides model, the #305 model, to fit on slim filters, and a more common snap-on cap.
It isn't an exact science due to all the variables involved, but generally a push-on cap that is 2-3mm larger than the lens' filter size fits just right.
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Comments about B+W #300 32mm Push-On Lens Cap:
Not only is it a generic cap, it's not 32mm. I only gave it one star because a rating was required for submitting the product review. My dial caliper confirms it's is just under 31mm. In short, don't order this cap. In an effort to acquire the correct cap, I now have three of them -- all identical, all the wrong size. In all fairness, it's not entirely B&H Photo's fault; I blame the manufacturer as well.
Displaying review 1
Displaying review 1
Pros
Cons
Best Uses
Comments about B+W #300 32mm Push-On Lens Cap:
Not only is it a generic cap, it's not 32mm. I only gave it one star because a rating was required for submitting the product review. My dial caliper confirms it's is just under 31mm. In short, don't order this cap. In an effort to acquire the correct cap, I now have three of them -- all identical, all the wrong size. In all fairness, it's not entirely B&H Photo's fault; I blame the manufacturer as well.
Displaying review 1