This reinforced guide stopper is what sits behind the spring guide. Upgrade the spring and the stock one might snap in half due to the pressure of the spring. Being reinforced, this can take the pressure of higher springs. If the stock one fractures, you could either ruin your plastic spring guide, damage the cylinder wall, damage the trigger assembly and sears or lock up your gun so you can't disassemble it without damaging your gun more.
Reinforced and very durable
Very expensive considering size, but worth it if you don't want to risk tearing up your gun if the stock one fractures.
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