Water Hammer - worn out arrestors?

[alex_mok]

Hello. When we remodeled our laundry room in 2015, the plumber installed an Oatey Quadtro washing machine outlet box, which came with water hammer arrestors (see picture). A few months ago, I began hearing water hammer (intermittently) and now pretty regularly. I'm guessing the arrestor(s) may have worn out or malfunctioning. I'm wondering if I can simply replace the water hammer arrestors, or since it came out of the box in one assembled unit, individual parts are not meant to be replaced? I tried to loosen one of them (see attached picture), but it's really on there tight and I didn't want to put too much weight on it in case it's not meant to be replaced. Should I go for it, put some muscle into it and pull the arrestor off? Does it matter which kind/brand to use as replacement? And, one last question, what do the different sizes mean (3/8, 1/2, 3/4) - pipe size I'm guessing, but they all look the same size so maybe I'm missing something (or I'm not looking closely enough). Thanks for any help.
https://www.oatey.com/2374361/Product/Oatey-Quadtro-Washing-Machine-Outlet-Boxes#prettyPhoto

 

[James Henry]

Hold the base of the valve with one wrench and take the arrestor off with another wrench.

 

[Sponsor]

 

[Terry]

Or the one on the left would fit with the hose. That way you could leave what is in the wall alone.

 

[Jadnashua]

When I installed them on mine, I put the arrestor at the washing machine rather than the valve. They work best when they are close to the quick acting valve (which is in the washing machine). They generally last longer than 4-5 years, but could be bad.