When choosing the right holster for your Glock, rely on quality that is proven by years and craftsmanship that has its work speaking for itself. Combine quality and tradition and you will have a holster that lasts a lifetime and you can rely on it as much as you rely on your gun.
Glock 21 is a kind of gun that can be holstered in any holster. As the versatility of the gun itself is wide, also the versatility of holsters, that are available on the market is large. To sum it up, you can choose from OWB or IWB holsters for your Glock 21, shoulder holsters, pancake holsters, paddle holsters, duty holsters, drop leg holsters, small of the back holsters, crossdraw holsters, concealed bags, ankle holsters etc. The variety is big, but the holsters always need to meet some basic criteria, they need to hold the gun in your possession, which means they have to have some sort or retention, they also need to protect the gun’s trigger to prevent accidental/negligent discharge and they need to grant you accessibility to your gun at any time as well. Other than that, then they can differ in finishes, materials, angles, carry positions etc.