Fibril variants maintain fibril morphology. We designed and produced fifteen different single point mutants of PI3K-SH3 to quantify their effect on the kinetics of amyloid fibril growth and the thermodynamic stability of the fibrils. These chemically conservative mutations span all of the seven β-strands in the fibril structure, the non-core region, as well as the inter-filament interface. In all of our experiments, we used seed fibrils made from the wild type (WT) sequence of PI3K-SH3, which forms exceptionally homogeneous fibrils under acidic pH conditions, the atomic structure of which we have determined previously . We have demonstrated that all the variants of PI3K-SH3 we made are able to elongate the WT seeds and do not alter overall fibril morphology, as judged from AFM imaging.