Samix TRX-4M Aluminum Shock Body Set with Brass Shock Spring Retainer. Intended as an upgrade for the Traxxas TRX-4M rock crawler this shock set offers premium components with performance to match. Constructed from CNC machined aluminum the shock bodies are strong yet lightweight and come with a durable and great looking anodized finish. They have also been designed to accept the stock shock cap, O-ring and shock shaft for easy servicing. Adding to the performance is a brass lower spring retainer. This spring retainer is not only more durable than the stock components but provides additional weight low on the vehicle helping to improve stability and climbing performance. Overall this shock body set from Samix is a must have for the serious rock crawler enthusiast.