These factory Glock 9 round .357 Sig magazines will fit the following models: G33.  They have a stiff metal tube encased in the proven Glock high-tech polymer. This resists deformation – even when dropped from great height or exposed to extreme environment conditions.

The XGrip Adapter pictured below may be of interest.  You use it with the full sized Glock 31 magazine giving you 15 rounds of capacity.

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XGrip Adapter for the Glock 26 or 27 XGGL26-27

$12.95