Your probably right. It states that it's for the 5908 slayer which uses shorter arms like 5931 vs 5931X. Leave it to traxxas to had 1/2" to something and resell it as awesomer. :)
Just got an email from MIP for a clearout sale. One thing that caught my eye were traxxas slayer slider cvd's for $15: http://www.miponline.com/store/mip09170.html
The other stuff: http://www.miponline.com/store/mipcloseout.html?mc_cid=91feb1189a&mc_eid=474c2edaad