non OEM shells are a mixed bag imo. The inner top and bottom shell parts generally always fit, the back top sometimes can be wonky, and the bottom back is pretty much always a pain to snap in right. Thats within a shell replacement set. I once reshelled one with the inner and outer parts coming from different non OEM sets, and that just didnt work, they would not snap together at all. Though they have a good price point, used DSs, even broken ones are expensive as hell. I personally use a non oem shell I got on ebay which works alright.