An adapter is provided which allows an external driving tool to drive a driven tool such as an intraosseous needle assembly, where the external driving tool would otherwise be incompatible with the needle assembly. The adapter includes a driver connector having a bore, where the bore is to receive an external driver of the external driving tool. The adapter further includes a driver attached to the driver connector. A cross-sectional shape of the bore is different than a cross-sectional shape of the attached driver. The attached driver includes resilient legs which assist in securing the adapter to the needle assembly. The resilient legs may include protuberances to secure the adapter.