10 round Compliance Magazine for the Glock 31 in 357.
About the Glock 31 10 Round Standard Capacity Magazine
Glock magazines have a hardened steel insert encased in high tech polymer. This polymer coating protects the magazine and prevents deformation, even when dropped from a great height.
Glock magazines have very stiff springs when new and may be extremely difficult to load to full capacity. It may be necessary to use a Glock magazine loader (generally included in the Glock case with the handgun) to load the magazine to capacity or near capacity.