Please refer to the attached picture as I answer your questions.
Setting up the magnetic filter system involves removing your lens from your existing lensholder and install it into the 25mm magnetic lensholder, shown in upper left in the picture. You will see 3 little round black dots around the lensholder ring, those are the magnets. This lensholder can be used whether you use filters or not, the magnets do not interfere with the lens in any way.
The second step is to add the magnetic filter holder to the magnetic lensholder, shown in upper right in the picture. This is the gray plastic ring with 3 corresponding magnets and a slot in the middle to hold the filters. This filter holder can be attached to (or removed from) the magnetic lensholder while you are wearing the glasses and the position is guaranteed to be correct due to the magnets.
The filters in the picture are, left to right in the middle row: orange, brown, gray; then left to right in the bottom row: yellow, 25% purple, 40% purple. I have an article explaining the use of different filters in various lighting conditions. Please see: http://www.precision-sports.com/custmset.htm. Those are guidelines, since no two persons have the exact same eyes or perceive color the exact same way, the effects of each filter may differ slightly from person to person.
Each filter is inserted into the slot in the middle of the gray plastic magnetic filter holder with the convex surface facing forward (target side), then put on in front of the lensholder using the magnets. When you need to change a filter, you have to take the filter holder off (but no need to remove your glasses), slide the filter out, slide another filter in, clean the lens, then put it back on the magnetic lensholder.
When you remove or insert the filters, you have to hold the front and back of the lens with your fingers using a piece of microfiber cloth to protect the lens surface. The same cloth, if clean, may be used to wipe the lens every time it is used.
The plastic filter holder when new is quite tight. The filters do not just freely drop in and drop out. You don't want a loose filter holder where filters can fall out of it accidentally. You have to push firmly, using a slight rotation or wiggly motion. Over time, once the plastic is conditioned, inserting and removing filters will be easier.
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