Nature2; can I use on this filter (link to pics)

[paulitzlee]

I have a really old spa I am thinking of getting upgraded.

Previously, Nature2 wasn't an option since the hot tub was only filtered when I physically turned on the jets.  With the upgrade, the water will be filtered whenever the heater is on and/or a certain number of hours per day.

So Nature2 MAY be an option.

My filters are large and have a lot of room in the "donut hole".  But there a long rod that goes thru them, then it's sealed with a screw.  Obviously the water filters thru, but now that Nature2 MAY be an option, do you think I can use them on these filters?  Even with the rod, the donut hole is a few inches.

I apologize for the duplicate pictures.  Google Picaso and I just weren't getting along today. 

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https://plus.google.com/photos/117935059108609701289/albums/6015675504341026673?gpinv=AMIXal9CuPveFb26dUeO3j7w0YBcDkChdkBryRmRMdLGiH5lvMT525SDNq_C0AnDkbBzsAjhWIWojBSPG-8FskPiqcsFuR2bjq7GMQu3dqAUX9mSNFLWYx4&cfem=1