You know that little half-moon shaped hole in the bottom of your Glock grip, the one that runs the back channel of the grip behind the magazine? Well, there is a lot of thought and energy that has been put into that hole. A lot of people like to plug it up and here is why.
There are several perceived advantages relayed by grip plug makers that include giving the opening at the rear of the Glock grip a cleaner appearance, keeping dust, dirt, snow, link, junk and water out of the gun, especially when carrying openly in a holster. It creates a perfect location for adding extra weight to competition guns or to counter recoil on light, carry guns. They are easily removed, and do not permanently alter the gun. They are even believed by some to help index mags by feel, which is useful in high-stress and low-light situations.
There is no limit of manufacturers for these plugs including:
Fits flush in the back strap channel and runs about $7. However, the LWD plug will not fit SF models; Olive Drab framed Glocks, or Gen4 pistols.
Long known for Glock accessories, Scherer produces its 'Slug-Plug' to fill (pun intended) the needs of Glockheads wanting to seal their grip cavity. They tend to run about $5 but like the LWD models, they don't fit Gen4 and SF models.
Jentra seems to be of the most popular grip plug makers. The produce no less than five different models (named creatively enough, JP-1 through JP-5) to fit almost any flavor Glock. These models typically sell through such websites as Brownells and Midway for about $7.
This company has always had their finger on the pulse of the Glock plug market. Other than Jentra they offer the widest selection and include plugs for both SF and Gen4 models unlike some other dealers.
And now for something completely different... Taylor Freelance sells a series of heavy, full-length brass plugs. These devices, dubbed Seattle Slugs, are more of a magazine funnel/recoil counterweight for both target and tactical shooters. Whereas the other companies sell a small plastic plug that weighs less than an ounce, the Seattle tips the scale at 3.5-ounces of brass. The things work so well that they are the only plug mentioned by name as being banned by for use in USPSA/IPSC Standard matches. They run about $30. They currently only make versions for Gen2 and 3 firearms but have a Gen4 "in progress."
Cons to grip plugs
Gaston Glock, the imminent inventor and chief engineer of the Glock series firearms left the gap for a reason. Speculation ranges from everything from it being a weight-saver as air is always lighter than plastic, being a drain for water and dirt to fall free via gravity (after all, some Glocks are capable of firing while submerged under water), shortening the manufacture process on the molded polymer frame, and others. Bottom line is, your pistol was designed to fire just fine without it and very few military and law-enforcement level users issue them with their Glocks.
I won't comment on whether or not I have ever used one, but I will pass on a comment from a fellow LE-level Glock instructor who has carried the tenifer-coated pistols for over twenty years and has spent more time at Smyrna than almost anyone I know.
"So Warren," I asked, "What kind of grip plug do you use in your Glocks?"
He shrugged, "The only thing I stick in the bottom of my Glock is the magazine."
To each his own...