Can also be referred to as Transverse Arms .. they attach to the subframe and the bottom of the struts.
You need two
Posterior (rear of subframe) and two
anterior arms (front of subframe) as they are different lengths.
If you don't know the history replace as a set of four.
BUT ... having done this recently you will probably need to replace the long bolts that run through the bottom of the strut along with the nuts. The bolt also has a spacer which can get stuck through rusting, so I replaced that as well. Plus all the lock nuts on the other bolts should be replaced as technically you should only use nylok nuts once.
One bolt is on a cam to adjust the alignment. You really don't want to move this one unless you have to. The other is not cammed but was a PITA on mine to move as you can't get the arm off between the end of this bolt and the fuel tank unless you loosen it.
I think I spend around £100(!) on nuts, bolts and other bits in the end!!! (but they may have included some front ones as I was working on that as well). That was on top of the arms!
And it took several hours, so don't envy you in this weather.
PS EB Spares
were cheapest for arms. Nut, bolts, etc I had to order from dealers.