Resin replacement mesh size

I've got a 13 year old GE water softener. Yeah, I know you probably all hate them but it has run flawlessly since I repaired the metering turbine 11 years ago. The softening capacity, however, is not what it once was and I'm assuming the resin may have reached the end of its life.

I coincidentally happened across some resin locally at a great price which I snapped up but didn't realise that I was buying fine mesh and this softener has standard mesh out of the factory. Can this fine mesh resin be used in the softener or do I need a new screen and/or gravel bed?

Yes you need the parts for fine mesh or you'll end up with resin escaping the softener into your plumbing and fixtures and appliances. An expensive and hard to correct mess.

A god awful mess. That stuff gets into the dishwasher solenoid, the washing machine, ice maker, toilet fill valves. It can cost a whole lot of money to have a plumber flush that stuff from the system.