thats why i love this site there are a lot of pros on this site who dont mind sharing thanks for the infoBird of Prey said:Jinkai is the smallest (I believe their 50# is .62mm). Momoi Diamond 50# is one of the heaviest 50# lines and rates at 83lbs (closer to the Jinkai 80# than the 50#). Regular Momoi Hi Catch is in between the two and a bit more supple than Diamond. All three are great lines (in my humble opinion), but different. I also find the Jinkai a little pricey (and I'm not sure it is worth the extra cost over the Momoi products).
Diamond 30# has close to a 50lb rating. I use it sometimes where a very thin 50# would be ideal. You might also look at Diamond 40#, which is as strong as most other 50# (I think it is .65mm and rates in excess of 60lbs). I spool my Tiagra 30LRSs with Diamond 40#.