Hi Guys, I have something very frustrating. After trying a lot of fans for the dual fan setup that I use on my UMOs, I found that it is very hard to find a fan that suits my needs: reliable, and PWM controllable (over two wires). I have tested with dual 25mm fans a while ago, but most of those fans are not PWM controllable (strangely, 2 from a batch of 6 actually were PWM controllable), so I switched to 40mm fans. All of my UMOs (7 in total) use a dual 40mm fan setup. The fans are from a random Chinese brand called 'Lyf'. The fans are PWM controllable and work fine. I also tried fans from a brand called 'MX' but those created so much airflow that the heater couldn't keep up. So recently some things changed. Fans started to make noise and burn out after a while. I ordered new fans from the 'Lyf' brand on Ebay and waited for a few weeks before they arrived. When I received the fans, I wanted to give them a try and guess what: the fans only run at full PWM! Apparently, a brand name doesn't say anything when you importing goods from China, because these new Lyf fans are not identical in operation as the old ones. This means they are useless for other materials than PLA in my opinion. I am sick of wasting money on all kinds of fans I can't use. Is there anyone who can tell me about a fan brand that makes 40mm fans which can be used on a 3D printer as a part cooling fan. This includes: reliability, but most importantly: PWM controllable over two wires. If you know a fan company that sells them for a reasonable price, please help me out. I have somewhere around 60 fans lying in a box, but I can't use one of them on my printers.