SYB H.A.R.D. is specifically designed to be used on devices that support a 3.5mm audio jack, and most versions of iPhones do not support 3.5mm audio jack. Thus, you will have to use an adapter to act as a bridge between the SYB H.A.R.D. and your iPhone, which can cause incompatibility issues.
If you have any additional questions, reach out to our customer service team at hello@shieldyourbody.com.