Excellent product this trolley is heavy silent and very solid weight ..and fortunately for stability and support while SLRs with big heavy lenses to bear ... the arm is required or tripod bracket extension because impossible to install a SLR ..sauf GoPro cameras or small ... 100% effective to make traveling table or on rails (homemade) with aluminum corner beads ... Only small flat where my judgment of 4 stars .. attention to tighten the wheel goods tend to be unscrewed easily. When the order and delivery on the top AMAZON !!! the best I know.