Do Thor Sentinel's have sizes or one size?

[2001Rm125]

Im looking to but a thor sentinel and some have sizes some dont. I need someone that has one to tell me if theyre one size fits all or not. thanks

 

[FruDaddy]

Thor website doesn't list sizes, and I am pretty sure it is one size fits most with and adjustable lower strap. I have one and had to let it out.