There were no instructions so squirt each hole with a little WD-40 and press very hard on the bolts to obtain the initial threads. Great product, easy quick assembly. It fit perfectly according to the size chart. (Except for the airpod pros)Much smaller than they look on the product page, which is a good thing. PriceSound qualitySoftware compatibleCons: The foam that they use in this version provides more of a seal. This item is a replacement item for a version that was previously available - they are the same type of trap (box) but for some reason these are not nearly as effective as those available previously. 5 inches long, Medium size is 8 inches long and Large size is about 8 3/4 inches long . This said, I basically pushed the tubes in unscrewed, and, in the companys favor, the larger holes for the tubes are well drilled and the tubes fit snuggly w/o the screws. I dont want to send it back due to the Amazon return policy. I oiled the locks to prevent the rusting issue.