Russian arms manufacturers have increasingly been adapting their weapons to use Western ammunition, and building their systems to NATO standards. For example, the Russian 2S19 self-propelled artillery system weighs 42 tons and normally carries a 152mm howitzer. But Russia now offers a version of the 2S19 that can fire 155mm shells. The 2S19 was introduced in 1989, as a more robust version of the standard 2S3 self-propelled artillery. The 2S3 itself was introduced in the early 1970s, a decade after the American M-109 self-propelled 155mm howitzer was put into service. The 2S3 was a direct response to the M-109. The two vehicles are very similar. The latest version of the 2S3 (the 2S3M1) weighs 27.5 tons, compared to 24.5 tons for the M-109A1. The 2S3 has a crew of four, compared to six for the M109. Max road speed for the 2S3 is 60 kilometers an hour, compared to 50 for the M-109. The 2S3 also has lower ground pressure than the M-109, making it more mobile in mud, snow and swampy terrain. The 2S3 also carries 46 rounds of ammunition with it, compared to 28 for the M-109. The 2S19 has all the basic characteristics of the 2S3, but has thicker armor and a crew of five men. This is because it uses the same chassis as the T-72 tank. The engine is multi-fuel, and the fire control and loading system is superior to the 2S3. The 2S19M1 uses a 155mm NATO standard gun, and is being offered to nations that want Western quality self-propelled artillery, but at about half the price.