The claimed weight of the 819 is totally crooked, they include the rim but not the little insert things needed to actually build a wheel. The true weight is 510g~.
"seanodav – Member
Is the 819 closer match to the flow than the 719? and whats the weight of them like compared?"
The 819's fairly similiar in purpose and strength to the Arch (apparently, never used one myself), just that it's heavier. People compare it with the Flow based more off weight but that doesn't work out. Mavic don't really compete tbh, they don't have an 821 but even if they did it'd probably be too heavy to compare since their tubeless XC rim is heavier than Stans tubeless AM rim. Flow is bigger, stronger and lighter.