Because fuzzies are 4.50 - 7.00 grams.
10% of my snake's weight is 7.07 grams.
Hoppers are 8.00 - 12.00 grams.
After reading the link dr del posted, it's better to offer prey a bit smaller then the girth of your snake. these hoppers are creating that "lump" noted below.
can babies go on off feed too? mine rejected todays feeding and my husbandry is within range. nothing new or removed from enclosure. however i have recently switched her to a 5 day feed cycle instead of 7. she had no problems the past 3 feeds till now. hopfully she will contine to eat on a 7 day cycle with these hoppers.Feeding
All of my ball pythons are fed once a week ... age or size doesn't matter ... Monday is feeding day at my "shop". I like to feed whatever my ball pythons will eat. Mice or rats, it doesn't matter to me as long as they are eating regularly and not losing weight. Unlike many of the larger species of pythons, I have had success feeding my ball pythons smaller sized food items ... rodents that are slightly smaller than the animals girth. I feel that feeding ball pythons too large of a prey item (one that creates a lump) will cause them to become "back up" and end up refusing food later down the road. I personally prefer to have my snakes eat more consistently ... and it's worked for me so far.
http://www.8ballpythons.com/journal/caresheet.htm