Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
Rio Grand is for fast action rods; it is heavier than the Gold line, and has more mass near the front of the taper. If you have a fast rod you might like Grand, otherwise Gold is a good all around line.
The RIO Grand is a full line size heavier than the industry standard, and features more weight distributed towards the front of the line to easily load faster action fly rods. The line has a short head that is easy to cast, and is built with "MaxCast" Technology, RIO's ultra-sophisticated line coating that actively repels water for higher floatation, longer casts and greater durability. The RIO Grand is the best choice of line for the modern, fast action fly rod.