The "D" Series offers up to a 30% savings over traditional NFPAdesigned cylinders using the same high quality components. We do this by sharing common engineering principles between bore sizes to reduce costs instead of offering any and all possibilities. Forexample, in the "D" Series we do not offer different rod sizes in the samebore, but we do offer different rod ends. This saves the cost ofstocking end caps with different combinations of rod and bore sizes asin an NFPA style cylinder. You get all the quality with exactly what you need.