I can offer you a 30 day guarantee (from shipping date). If you have any problem with the cartirdge that we cannot resolve online then I am happy to take back the cartirdge and refund you the purchase price (excluding shipment fee). Conditions for the guarantee: after the receipt of the cartridge back (you have to cover return shipment) an inspection will be carried out by Ana Mighty Sound to check if cartirdge has been returned in the same condition as it was sent to you.