Tasty is on point as usual. Unless you know someone in Germany (privately, not a company) that can pick one up for you and send it to you, it is really tough to get. Any firearm part over the cost of $100US dollars needs to be reported to the ATF or something or other if shipped in from a foreign country. I'm probably a little off on my info, but its generally the reason why the Merkel Tuning Weight isn't readily available to get here.http://merkle-tuning.de/baseportal/the_site/Products/P_detail&ID=42
Ralf Merkel is a pistolsmith in Germany. He specializes in revolvers mainly S&Ws. He's also quite an accomplished competition shooter. He makes accessories for revolvers and autoloaders. The weight is designed to reduce muzzle flip and allow the shooter to get back on target faster. The main problem with getting his products is US import laws.