This is a 4" Sack-Ups pouch shown with a standard sized 91mm (3.5") Swiss Army Knife -
The size (obviously) refers to the pouch part and the total length of a folder closed.
The pouch part barely fits this knife - there is a so-called flap which never seems to want to stay naturally closed -
but it is ideal for extracting/pulling the knife pouch from the pocket - so I consider what probably is a design flaw a real advantage as a knife pouch for pocket carry.
Do a search on Sack-ups (note the spelling and hyphen) with
www.Froogle.com to find vendors and prices.
eg:
http://www.bladematrix.tv/shoppingmatrix1/sack-ups-case.html
http://www.theknifestore.com/sackups.html
(Note: I have not dealt with either of the above vendors, so can't comment on them)
The one above in the photo is a 4" knife pouch that comes in a 6-pack Model: HS 805
other model #s -
3" 6-packs - HS 804
5" 6-packs - HS 806
2x 3", 2x 4", 2x 5" - HS 803
I had not noticed the Sack-Ups for FIXED blades -
but these seem to be the sizes:
Sack Up 810 Knife Pouch holds 4" fixed blade knife
Sack Up 811 Knife Pouch holds 5" fixed blade knife
Sack Up 812 Knife pouch holds 8" fixed blade knife