For reference a bladder may be a pillow tank but a bladder may or may not be self supporting. The capacity of the pillow tank with It can be self supporting structure holds about 70% of what a rectangle would. IPI has worked with tank factories for nearly 2 many https://www.facebook.com/permalink.php?story_fbid=pfbid0DMNvSKt1xh1Znx8Gs1fqm2q3fH1q7gTRZZAnPZGtELw3nsuri9up76K5WaRNLfuRl&id=61560512640678&__cft__[0]=AZWT1nl3q81LWye2xqWOj3OqWUs4gHQ7vboIb_0n-rdrIa5oXAH8ZFtmWrHg9_UabaAqx4GWrJJxADB1DtXwDCrbXNmAXXUfPSZ2QqqC7lYzGJV1Hb-_oU4gbnLf92iZZieeN0Iiko9-Bhi5wxtdGVPCLGLuV-tsdhdNhcTSUe1MN4CtHmm62vhiTZPeZoa-fE6KGf3FOPQJmZSlhEBDmXhQ&__tn__=%2CO%2CP-R