3/16" ball links and balls are the most common and can be used on nearly every helicopter flying today. These ball links are a direct replacement for all JR helicopters. The nice thing is these links are nearly a perfect fit to the JR ball requiring NO sizing for a slop free fit! For other brands of helicopters, these links can be sized to fit the existing ball or re-fitted with a FMP Ultra ball for a perfect slop free fit. If you require the most from your helicopter and the control system, you need FMP Ultra Ball links and FMP Ultra ball link balls.