Servo77
All 870's are now supplied with Polymer (pronounced POLLY-MYRE) trigger housings. At first I scoffed at this cost saving measure, however as the years have rolled by it looks like a good decision. they don't ding or scratch like the aluminum housings and the high wear areas inside the housing are steel bushed as with the aluminum models. If you really want a aluminum trigger housing, they are out there, not sure you gain anything in the change out.
Good Luck and be safe