Rotary pneumatic actuators convert the energy in compressed air into rotary torque. This is typically achieved using pistons and a linear to rotary conversion either using a rack and pinion or scotch yoke system. AVS prefer the rack and pinion system as it does not lose too much torque in mid travel, which if it did, could be an issue in modulating applications.
The principal brands offered by AVS are CH-air, Prisma and Max-air, all European brands, each with many years of experience in the pneumatic actuation markets, and each with their individual features and benefits, and enables AVS to offer aluminium, plastic and stainless steel pneumatic actuators. Very healthy stocks are available either from the UK, or in bulk stocks in western Europe.