2008 Suburban

Any idea what type and size this bolt is? The arm rest is so loose it spins 360 degrees.

Picture below of bolt.

Thanks

 

1/2” deep socket. My kids playing messed it up where it was flopping around the bottom of the seat and wouldn’t come to a normal position. Loosened it to the point that I could move it back to a normal position then tightened it down. Like new now.