The Opemus 5 enlarger has the same negative carrier as the 3 and 4. The negativecarrier is made of metal and will convert from 24X36 to 6X6 when replacing some inserts with a glasscarrier works great for me ( then again I got two

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some of the cheaper Durst have plastic negcarriers that I find ........ cheap.
They are pretty common, at least here in DK. You may still find parts for it new but you can often get another enlarger for a song to use as spares if it should become necessary. That said it is not that fragile and there is few parts in it.
Mine came with the colorhead and the lamphousing. I don't use the colorhead because of its weight and because I don't find it worth bothering with. The weight of the the colorhead made the enlarger more unstable IMHO, partly because the baseboard is not that thick.
I don't know about the anaret optics but if you want to use 50mm lenses with 39mm tread (el-nikors) you might be in trouble. They need recessed lensboards and I have yet to find one that will take my El-nikor and fit the Opemus 5.
Since I use Schneider Kreuznach lenses now for both 24X36 and 6X6 that is no problem for me but you should be aware of it. All in all I like the Opemus enlargers, they are simple, light and fairly sturdy, Not like german panzers but they are good enough for me. You can find enlargers that are better eg Besseller and more expensive Dursts but will they give you more value for money ? I don't think so, at least not as a beginner.
Did I leave something out ?
Regards Søren