The Replacement Inserts Compatible with CAL389 100 Engines are a great addition to any automotive tool kit. Based on my observations, these inserts are made of high-quality materials ensuring durability and longevity .The precision ENGINEERING ensures that the fit is perfect, providing a seamless repair process. The only downside is that the price may be a bit steep for some customers. But overall, these inserts are a must-have for any serious automotive mechanic..