Yeah, the armbands and flashing vests that I've seen are quite dim compared to even mid-range current tech blinkies. You need only look at the batteries they use and the stated run time - the popular one I've seen claims 168+ hours from two AA cells - so clearly they aren't putting out a whole lot of light - something on the order of PBSF but spread out over a large area and divided in half for front and back. And their reflectivity isn't great either, they use that prismatic vinyl which is mediocre at best compared to proper reflective material.