ARC Synthetic Resin is a Rare item that you can find by defeating ARCs that wander around the map. As a Rare item, don't always expect to find it on any of the smaller enemies, like the Wasps, ...

The Aphelion Rifle is a legendary weapon that you have the chance to acquire in ARC Raiders. Similar to all guns, there's a blueprint version that has the possibility to drop, allowing you to craft it ...