You can't describe SHS gears without using the words tough reliable and affordable. For ultra high torque and speed setups techs love the toughness of SHS gear sets. Some of the craziest setups out there use them (with other SHS parts of course). Their reliability comes from the high precision manufacturing process where they are CNC machined. However their affordability separates them from the rest of the pack. Most people don't know you can have the performance of these gears at this kind of price. Perhaps this explains SHS's growing reputation among both technicians and the common airsofter for doing a high performance upgrade or a reliable repair.
For M150 springs and under.