These ae brand new injectors with ridged o-rings, not smooth like BassTackle on the plunger. The O-rings on the caps are smith like BassTackles. The extra o-rings that came with them are ridged too. I will look for smooth replacements, however it is where and the correct diameter. The o-rings are larger than BassTackle. The Ultra Mold injector will get me by until the new ones arrive.