This guide will let you know how to unlock the Lost MC Biker Outfits in GTA 5 Online.
The first mission you are going to do is Lab Locations. When you start this mission, you will receive a text from Sessanta, as shown in the image below.
After that, you will find a slamvan spot on your game map; you have to go to the MC clubhouse and kill all members. Then you will need to grab the Slamvan and leave the place.
You have to drive this to the clubhouse, open the van back door and then grab the lost MC outfit. After grabbing it, you will see that you have easily unlocked the outfits. So you need to go inside the clothing shop and find your new outfits there. There are four different lost MC outfits, so it is how you can unlock the Lost MC outfits, as shown in the image below.