When you need to repair your Hypro D303 or D403 pump, make sure you have this 9910-KIT2389 D303 D403 O-Ring Kit on hand. It contains all the O-rings you need to repair either model of pump, for a grand total of 30 O-rings for the various parts of each pump's assemblies. Be ready at any time to fix your pump, and reduce or completely eliminate downtime in your sprayer systems.