I traded an almost new Sigma 100-400 for a Tamron 100-400 for the sole purpose that the Sigma wasn't designed to take tripod collars. The "excellent" Tamron I received was broken, autofocus won't work. From there, things got really interesting, since they won't give me back my Sigma (can't be done because of property transfer) but I can buy it back, almost double the money I've sent it for (yes, they are willing to refund me the amount I've trade it for + the extra fee I paid for the Tamron) Tried talking to a manager who got time for me a day after, and since doesen't replied my response. Since we are both based in UE, I will both contact the ECC, SOLVIT and my attorney, since I've sent back the lens (so I'm transfering the property ownership back to MPB) but they won't send me the lens back and refund me the money. They offered me a discount but with that discount I still pay more for my lens back. For me is a scam and I can't recommend anyone buying or trading with them. As of yesterday, no reply from the manager who finally got the time to talk with me, to which I responded instantly and I tried different aproaches so that both me and MPB doesen't lose a dime.