Perfect thanks. This one little detail that is quite significant IMO as we continue to perfectly advance our miata to the next generation. Funny is that polyurethane makers does not even recommend this and so I have not seen it mentioned in the manual plus they supply the white silicone so if no one research on this it is a knowledge lost as common practice dictates that you do what manufacturer the recommends. Polyurethane without the squeak is a very good bushing alternative, affordable (cheaper than stock bushing) and easy to install (no press required). Just make sure you stay 80 or less durometer. With factory coils and shocks you would hardly feel differences in NVH (noise ,vibration and harshness). But with aftermarket coilovers or stiffer springs and shocks combo then a slight tightness on rough pavements can be noticed.