I have bought a lot of Nielsen frames from Best4frames in the last few years. They are best prices I have found online. They pack the frames really well so everything arrives in perfect condition. . I buy quite large frames from them, up to A1 in size and I have only recently had one frame which arrived from them which wasn’t perfect -a manufacturing fault. I advised them of the problem and they immediately sent out a replacement and sent an email to say sorry and a new one was on the way. Excellent customer service. I have recently used their bespoke mount cutting and the mounts are excellent quality too.