|Glock 17 and Glock 19 with Scherer Slug Plugs|
For 17/22/24/31/34/35/37 Gen1, Gen2, and Gen3 frames, it's great. Helps keep magazines from hanging up on the web at the back of the magazine well, and keeps dust and junk out of the action. Will not fit SF frames.
For 20/21/19/23/32 Gen1, Gen3, and Gen3 frames it doesn't quite fill the void entirely, but it does fit, and is an improvement. Will not fit SF frames.
You can get away with them in some IDPA matches, but not for others. It depends on whether the person reading the rulebook:
- Places the exclusion of "[e]xternally visible modifications other than grips or sights," rule higher than the allowance of, "[p]lastic plugs may be used to fill the opening behind the magazine well."
- Considers the Slug Plug to be a magazine funnel
- Considers the Slug Plug to be a modification of the grip or a part added to the frame
Plugs that extend below the frame, are not allowed in USPSA Production division. You may be able to get away with them in some club matches, at the discretion of the people running the match.
I would use the brass plug from Taylor if I were going to carry a 3rd Generation 20 or 21. The Taylor plugs fill the void better. The brass plugs are specifically disallowed by IDPA rules, though.
UPDATE, 8/21/2010: Added Photo
UPDATE, 5/26/2013: Added that Slug Plugs may or may not be IDPA legal. Change link to Taylor Slug Plug. Note that the Scherer plugs do not fit Gen4 or SF frames. Add notation on USPSA production with link to NROI ruling.