Reddit mentions of Genuine GM Bulb Part# 23342527

They are good bulbs (the Sylvania XtraVision 9012).

Funny thing is that they were actually commissioned by GM. For the 2014 and 2015 Silverado, GM put in such shitty headlamps that owners said the previous generation was better (and Silverados have never had great lamps).

GM faced lawsuits and they literally had to go begging a German company to create some special high-performance 9012 bulbs to compensate for GM's shitty headlamp design. Plenty of vehicles use plain-old 9012 bulbs without any complaints, but GM fumbled the headlamp design so bad that they needed a 9012 bulb that put out literally 30% more light in the beam pattern to please owners.

Now, these high-performance 9012 bulbs with 30% more beam flux are readily available for cheap. You can get them under the Sylvania XtraVision brand. Or you get them in a GM/ACDelco box from this link, or you can go to your local GM dealer and ask them for part number 23342527.

Note that GM did not grab some Silverstar zXe bulbs to put into the Silverados, but instead had to pay extra for a company to make a special line of bulbs that didn't exist before. There's a reason GM didn't go looking for Silverstar bulbs--GM knows that they're ripoffs. Overpriced and underperforming--they don't put out more light than standard bulbs--they actually put out significantly less light than standard. People think they put out more light because the slightly bluer light from the Silverstars plays a psychological trick on us: we perceive bluer light as being "brighter." That's why people moan about how someone's HID/LED headlight blinded them on the road. But the scientific reality is that the bluer light does not actually cause harm--the bluer light increases our sensation of glare, and makes us feel blinded, but our reaction time is not affected.