castnet diameter measurement

I just received a castnet from Ebay that was supposed to be 10' but the diameter of the weight ring is actually 6'. The measurement from the weights to the center is 5' however and the seller is claiming that that makes it a diameter 10' net.  What is the correct way to measure castnet size?

If it's 5 ft. tall it opens to 10ft...if it's 3ft tall it opens to 6ft...

The standard measurement is “radius”, but I put that in quotes because most nets, at least the cheap ones we are willing to throw in the rocks where the herring spawn, won’t open to a diameter that’s twice the radius. For example, I have a cheap 5 foot net which does measure 5 feet from the horn to the leadline when you hold it up, but if you spread it out on the ground it only opens to a circle 7 feet in diameter, or 8 feet if you weigh down the edges and stretch it.

Even given all that, I would be pretty disappointed to buy a 5 foot “radius” net that only opened to a circle with a 6 foot diameter.

On a thick spawn I don’t mind not having the full diameter and purposely throw it so an so. It’s hard to pull a full net over the railing.
I have a 6’ radius and on a good throw it might open 8’

flipping flapping flopping popping hopping herring!

What size would you recommend for first timers?

5’ radius

The standard measurement is “radius”, but I put that in quotes because most nets, at least the cheap ones we are willing to throw in the rocks where the herring spawn, won’t open to a diameter that’s twice the radius. For example, I have a cheap 5 foot net which does measure 5 feet from the horn to the leadline when you hold it up, but if you spread it out on the ground it only opens to a circle 7 feet in diameter, or 8 feet if you weigh down the edges and stretch it.

Even given all that, I would be pretty disappointed to buy a 5 foot “radius” net that only opened to a circle with a 6 foot diameter.

Mine is actually not that far off from what you have. If I stretch it, my "10 foot net" has a diameter of 6 1/2 feet, just 6 inches less than your 10 foot net.  One difference with these nets that don't open to twice the horn-to-leadline distance is that when you pull them up the diameter doesn't contract right away because their fully open shape is a cone rather than a flat net.  A net that expands to the full diameter would have to contract immediately as soon as you start pulling on it. I've yet to use a cast net but wonder if the technique for these smaller-diameter (yet full size horn to leadline) should be different. Pull up earlier maybe, since it won't contract until you stretch out the net into a cone?