Bower filters are often 'included' as inexpensive sweeteners for those unaware that there are other products that do not deteriorate your image qulaity to the same degree.
Really good filters are
- absolutely planar parallel glass, so they do not distort the image like a prism
- highest quality optical glass
- using multicoatings to maximize light transmissuion to 98-99.9%, not single coated with only 93-94% transmission
I would buy Tiffen before I bought Bower, and I would not buy Tiffen!