Like Old Hair Twister, I bought a brass one also, but it was from Pam Damour, the Decorating Diva. It looks like the same one offered from Eleanor Burns, but Pam's has a lifetime guarantee with it. There is an address to send it to should it ever need sharpening. Watch her video to see how to actually RIP the seams, not pick threads. It works like a dream and saves time. It was $26 with shipping but worth every penny.
http://www.pamdamour.com/proportional-scale-clone.html