Peterbilit all models with rear air springs except Tow Trucks Rear Timbren SES Suspension Helper Kit ; 16000 lb. Rating ; Timbren Suspension Kits (SES Kits) are designed to enhance the suspension of your vehicle to prevent vehicle sagging and swaying when carrying heavy loads, towing, plowing, and using a slide in camper. The rubber cushions absorb road shocks and automatically adjust to uneven loads or road conditions. There are no airlines or fitting to allow leaks. Guaranteed for the life of the vehicle. Most kits can be installed in a matter of minutes using basic hand tools. Timbren's high performance suspension packages will ensure added safety and peace of mind.