Actually there often is, but you have to be a little careful.
For example, Manos del Uruguay is not the same thing as Malabrigo. I think I could be forgiven for assuming they were similar. They're both aran-weight wool. They are both from Uruguay.
But Malabrigo is Merino, and Manos is a mix of Merino and Corriedale. Corriedale is a firmer, less soft yarn, and it wears better. But it also — I know this from knitting a beret out of it a while back — isn't as compressible. It's stiffer and kind of fiber-y.
Another hint is that the yardage isn't the same. Malabrigo has 210 yards in 100 grams and Manos has 138 yards.
Well, I didn't take these hints. I thought "Uruguayan wool, aran weight, both can be knit at 4.5 spi" and tried to knit Mary Keenan's Not-Just-For-Chemo Reversible Cloche with some lovely Manos del Uruguay I had.
And worse, with the wrong kind of needles. I used US #3s for the brim, but I needed size US #4 dpns once I got past the linen stitch, and I had very short Inox ones or long Comfort Zones. Comfort Zones are great needles, don't get me wrong. But they are not a good choice for fibery wool when you are trying to knit at a gauge considerably firmer than that for which the wool was designed. They catch the yarn constantly on their tips, they make a horrible scratchy sensation every time I go through a stitch, and they got very bent, because I was trying to make them force the yarn into submission.
Anyway, this was a hard knit. Worse, I screwed up the brim several times and had to start over. But I promised Ronise a chemo cloche from this yarn and so I was damned if I was going to give up!
It's actually getting close to done now, and there is just one problem — it's coming out too small. I am hoping to hell I can block it out to fit her, because I am just NOT going to knit this again. Very, very cute pattern. Linen stitch brim: big pain in the butt.