sangel said:some are 11 cm in diameter (35cm circumference). It can be bigger ?
Yes. The largest Hip. bulb I've held in my hands and grown to flower was this one, at 39.75 cm. I purchased locally, and to quote myself when it started blooming: "Oh My...What a show!" Very pricey, and FWIW, I regularly check the bulb size (circumference, in centimeters) when I purchase and compare it the 'promised' size stated by the retailers before planting.
Online retailers / local shops are starting to sell 'jumbo' or 'XL' bulbs for a premium. So yes, they do grow bigger. Would they grow that big in your own care? Is it only special cultivars now being bred for these bigger bulbs? Would any regular bulb get that big under prime conditions? Time will tell, but the huge bulbs I have are H. 'Red Lion' and 'Black Pearl' ('red pearl?') two common cultivars. Royal Colors offered in 2019 a "Super XXL Jumbo H. 'Akiko' " bulb of 46 cm + which they claim is "The Largest Amaryllis Bulb on Royal Colors" . I've never ordered from them, so I can't say anything about it other than the size claim.
~ken
