These lightweight steel rods are machined from Chromoly steel (EN24) and are almost 250g lighter than the standard rods - almost a kilogram (2.2lbs) lighter for the set.  The rods are fitted with ARP 2000 bolts, balanced, shot peened and have been well proven, a great upgrade for a tuned or competition engine.  Supplied with ARP Moly lube and bolt tightening instructions.  

The little end (wrist pin) is tapered so will suit the SE type pistons and has cheek reliefs to provide oil spray to the pins - as per the later Lotus engines.  

The Lotus 900 series engines are known to have something of a "flexible" block because of the open deck design, the standard engines are fitted with very heavy connecting rods, pistons and flywheel - which when spinning with the crank in a running engine can exacerbate the flexing of the engine block.  Lightening the reciprocating components (rods and pistons) helps to lower the stress on the engine and make for a more reliable and smoother running engine.