For several years YSeq.net has offered a very good I2a-M423 panel which covers almost every important SNP for I-L621, I-CTS10228 Dinaric, Disles, and I-L161 Isles. Today YSeq introduced a SNP panel that is for the I-M26 "Sardinian" branch, the I-L233 "Western" branch and the smaller branches like Alpine, Northern France, France etc. Here is the link: https://www.yseq.net/product_info.php?products_id=51639 Of course, many members of the I-P37 project have already done Big Y tests, or extensive SNP testing and you don't need any new tests. But I recommend this SNP panel for many people in I-M26 "Sardinian" and I-L233 "Western". It's much more complete than the I2-P37 SNP pack at FTDNA. It's also cheaper ($88) but you will need to give a new cheek scrape DNA sample (there is a $5 kit fee) and you will not be able to add your YSeq results to your FTDNA page.
I can also recommend this test to I-P37 men who have done tests at other companies and don't wish to order tests at FTDNA for whatever reason.
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