RPM T4 & B4 gear covers are completely sealed, preventing even the smallest particles from entering the gears. The spur area of our T4 & B4 Gear Cover has been slimmed down for the wing on a B4 to fit over without interference. They also come with two 4-40 SHCS mounting screws that eliminate the stock button head screws. This means easier access to the pinion & spur gears since the gear cover can be removed using a ball driver - no removing the tire to get to those tiny button head screws! This gear covers also come with our oversized, soft plug for quick and easy access to the slipper adjustment nut for instant trackside adjustments. RPM B4 & T4 Gear Covers are built from our trademark blend of bulletproof nylons and carry our lifetime warranty against breakage. They are available in either blue or black to suite any individual's taste.