[NSFW] Body part sizes tags

Tags describing body part sizes need to be standardized, this is important for filtering them out/watching. Description that I’m providing below are heavily based on those from e621 or just the same, links to e621 wiki pages are in brackets.
 
On e621 for breasts there are those tags:
 
flat chested (e621) - no breasts at all, flat chest.  
small breasts (e621) - below average  
medium breasts (e621) - average  
big breasts (e621) - big but smaller than character’s head  
huge breasts (e621) - equal or bigger than head but still plausible  
hyper breasts (e621) - too large to be psychically possible
 
source: https://e621.net/wiki_pages/187
 
For penises:
 
small penis - no description, but well, smaller than average  
penis - there is no tag for normal size, it’s just penis  
big penis (e621) - large penis but still psychically possible, reaching past the navel/upper abdominals or thick enough that fingers do not touch thumb when grabbing  
huge penis (e621) - longer than 1/3 of characters height/lenght or thicker than half the character chest width  
hyper penis - no description on e621, but just as any other hyper:
 

 
https://e621.net/wiki_pages/49
 
For balls:
 
small balls (e621) - small than usual, size of an eyeball  
balls - there is no tag for normal size, it’s just balls  
big balls (e621) - bigger than usual, but still realistically possible, not much larger than a fist  
huge balls (e621) - significantly above average, too big to be easily held in two hands but not big enough to sit on  
hyper balls (e621) - unrealistically large balls, larger than 3/8 of a body, character can sit on them without other support
 
And similar things for other body parts. Then there tags describing how fat a character is:
 
slightly chubby (e621) (on e621 chubby is aliased to slightly chubby for some reason)  
overweight (e621)  
obese (e621)  
morbidly obese (e621)
 
detailed description of those four is at https://e621.net/wiki_pages/2241

This was so far my personal take on breasts:  
• flat chest - just like on non-obese males  
• small breasts - more than flat, smaller than fist size  
• breasts - no specific size tag, from fist-size till you can’t easily tell it being smaller than head anymore  
• big breasts - +-the size of the head  
• huge breasts - notably bigger than head, but still in the limits of realistic  
• hyper breasts - anything above, probably more than two to three times as big as heads, weapons of mass destruction  
Note: The view of many people on breasts and genitals is skewed by porn. Breasts as big as heads are already over average, so that checks out from what Cru posted. But the the adjective “average” is bad, way too subjective. Fist-size is more descriptive and you can quickly put your own fists in front of you to check.

 
Comment to penis:  
Just as breasts, the penis size is skewed in people’s minds thanks to porn. An average human penis is 14-15 cm long when erect, (measured on the top side from pubic bone to glans in a 90 degrees angle from the body). So a penis that reaches the navel, is already slightly over average. Big penis from navel on, as Cru posted, seems sane and checks out too.
 
Micro penis is under 8 cm under same conditions as above, I would tag those as small penis.