The RS-100 boxes accommodate the 223 family and similar cartridges
and have a hinged latch (without handle). The R-100 series boxes work
for cartridges with a 308 case head thru most belted magnums. These
have a handle, adjustable tray, and cartridge “fingers” to secure rounds
that are stored in the bullet down position. The R-100-MAG boxes work
for your WSM’s, WSSM’s, Short Ultra Mags, and Ultra Mags.
Sinclair, Issue:4A, Page:127