Designed with a extra heavy-duty wire harness durable enough to serve the demands of mountain bike enthusiasts, the SI 90 is an example of proven reliability. Go ahead, ride your hardest. The SI 90 will keep up with you through every turn of the crank. The SI 90 is a fully functional cycle computer, housed in a waterproof sonic-welded casing. Perfect for all riding conditions, the SI 90 will be along for the ride for many miles down the road. The question remains, will you?