Hostile now offers their axle boots in a choice of 2 different materials. The original black boots are made of natural rubber, are very elastic and resilient but require the use of 100% synthetic or silicone based grease as petroleum based grease will soften or swell the material. The new gray boots are made of high grade urethane and are inert to all greases allowing the use of any available grease.

The gray urethane boots are not as elastic as the black rubber but offer a good option for those that have had issues of softening or swelling of the black boots. The lessened elasticity of the gray boots does not allow the use of an install tool.

Information to help you choose your boots:
 
Black rubber boot:

-Elastic and resilient to tearing
-Very resistant to fatigue over a longer period of time
-Not for use with petroleum based grease
-Tested and approved greases are Team Fast Eddie grease, Lucas Oil Red & Tacky #2, Permatex Silicone formula Ultra disc brake caliper lube, Wurth silicone lubricant.
 
Gray urethane boot:

-Cut resistant
-Allows use of any grease type
-Less elastic so use of an install tool is not suggested.

Important information regarding use with Dark Soul "Toobz":  The trimming required for use with "Toobz" eliminates the locating feature that places the shock absorbing feature of our boots in the proper location. Using this combination may affect the function of the boots.