so i finally installed the twistep...it is awesome!!! BUT... it is only held on by one screw...no nut...no nothing...a little concerning to me anyway...it works awesome..it is so big that the dogs just jumped right on it...well worth the money...anothe r BUT...if you are putting it on an SUV with the 610 model (i think that one is the suv) it works well... i have the 510 model...and it is great...but your truck must have a stiff rear end...if not, when the dog jumps on the step, the step moves down about 4-5 inches...no big deal, it doesn't scare them (titan is scared of shadows mind you...and trash barrels) and he was fine on it....I would definitly get one!!!