Rotary Subs are made from 4145H Modified Steel Alloy with quenched and tempered to 285 ~ 341 Brinell Hardness as per API Spec. 7-1. They can be used to crossover from connection size to another or as the disposable component used to extend the connection life of a more expensive drill stem member. Crossover Sub ( X-over Sub) The Crossover Sub is for crossing one connection of BHA over to another connection. Lifting Sub Lifting Sub enables the safe efficient handling of straight OD tubulars such as drill collars shock tools jars directional equipment and other tools by using the drill pipe elevators. Saver Sub Saver Sub is attached to the bottom of the Top Drive System or Kelly Bar. Those two spots are where the drilling string is made up or broke out most frequently.  That means the Sub receives most amount of wear.  The Sub is easily repaired or replaced an extra saver sub in rotation is good to protect the Kelly . Straight OD Sub Straight OD Sub is used to connect drill stem tools that have a similar outside diameter. The drill bit downhole tools heavy weight drill pipe and drill pipe can be crossed over using a straight OD sub. Reduced Section Sub Reduced Section Sub is used to connect drill stem tools which have different diameters that warrant the cross-sectional change necessary to accommodate different connections. This sub would be used to crossover large OD drilling tools or a tapered drill collar string.