Callies has developed the Ultra connecting rod with the design goal of an uncompromised strength to weight ratio. Every Ultra connecting rod is produced from specially formulated Timken 4330 steel and precision forged for uniform grain flow and consistency. Many geometric nuances are incorporated into the design of Ultra connecting rods, which are subject to high output, high RPM applications. These design features enhance the Ultra against specific loads and stresses.

Ultra connecting rods are fastened by high alloy cap screws produced specifically for severe applications by ARP. Purpose built 260Ksi Ultra Bolts offer improved thread engagement for a smoother, more consistent net clamping load. To eliminate deformation and extrusion only Ampco 45 bronze silica alloy is used within the wrist pin housing bore. This material has a proven hardness more than 26% greater than commonly used Ampco 18 material. For high RPM or extreme horsepower applications, Ultra connecting rods are fitted ith MP 3.5 bolts. These Ultra high alloy fasteners provide unparalleled clamping strength and toughness. Upgraded bolts are available for all Ultra I-Beam connecting rod configurations.