In 2015, FTDNA began offering bundles of 100± SNP tests for ~$100. These bundles, called "SNP packs" are individually designed to test relevant SNPs for particular haplogroups. For a list of them and their contents, refer to this page.
Mike W has granted us permission to publish here his opinion of them.
From: ISOGG @ yahoogroups.com
Sent: Friday, September 18, 2015 4:05 PM
To: ISOGG Yahoo
Subject: [ISOGG] New breed of SNP Packs from FTDNA
The newer SNP packs coming out from FTDNA are more robust and multi-purpose.
All of this depends on the pack and its design, but I think we've seen a glimpse of this in new R1b Packs for Z255, L513, DF41 and L1065.
Packs are NOT a haplotree dependent bundle of SNPs. They can and should include key and lead SNPs that mark branches on the tree. This drives haplogroup assignments for project and matching screens. However, packs can easily have 100 SNPs in them and the nature of the packs are that everyone gets tested for everything in the pack, all in one fell swoop.
This can help prove branching for formal trees like the haplotree.This is very useful in combination with the project Y DNA SNP report screens.
The all in one fell swoop approach can help discover new branching among existing phylogenetic equivalent blocks of SNPs. Phylogenetic equivalent blocks are temporal in nature. They are only equivalent "so far" but at any time, the next individual tested can bust a block up. Many of the equivalent SNP blocks discovered via Big Y are only tested by a handful of people, some times only two people. A properly designed SNP pack can help exercise equivalent SNPs to see if additional branching can be discovered.
Packs can include SNPs "under investigation" to give them a good workout and provide more information for applicability to formal trees. Some newly discovered SNPs may be marginal and need further testing. BAM file interpretations are not called interpretations without reason. Chromo 2 SNPs or those discovered only by FGC or YFull are good examples too that might be included in packs.
However, keep in mind that Next Generation SNP discovery testing is what drives the availability of all of these new SNPs for these packs. A test like Big Y is still the best way to go for those who can afford it.
We think these are the "takeaways" from the above.
In case you're not familiar with some of the terms, here are some definitions: