I Got Butt Implants That Are Round and They Are 375 Cc's and Look Flat?

The most important guideline to use when determining the size of buttock implant is simply the anatomic dimensions of the patients pre-operative buttock muscle and buttock cheeks.  Any  implant much larger than the height and width of the buttock will just not fit, at least the first time around.  After successfull initial placement, the patient may opt to come back in 9 -12 months to have a larger one put in.

Keep in minf that the largest (legal) buttock implant available in the USA is a 690cc round implant made by AART.  Indeed custom implants can be ordered larger, not only at a premium price but at a premium risk for most patients'.  Unlike breast implants which are placed under the very expandable tissue of the breast and half of the pectoral major muscle, buttock implants are (most preferably) placed under (or at least within) the largest strongest muscle of the body, the gluteus maximus muscle, which is not nearly as expandable or forgiving.  Thus most patients simply do not have a large enough native buttock muscle to fit an implant much over 400 ccs' the first time around, without leading to significant complication such as wound breakdown/opening &/or implant exposure...necessitating removal.

Glad to help... @drryanstanton

Intramuscular implants can improve volume by 400 cc or so, depending
upon the size of the individual. A significant amount above this
volume compromises healing by creating more tension on the healing
incision.Kenneth Hughes, MDLos Angeles, CA

Implants are placed based on preoperative measurements of both height and width.  If larger implants are placed they not only look unnatural, but have a high percentage of complications.  When one weighs the complication against a potential benefit then it is easier to aire on the side of being conservative then to accept an unnecessary risk.