AR-15 rifles that have been converted to shoot .22lr are a great and inexpensive way to shoot. Unfortunately, when a standard AR-15 is converted to .22lr through a conversion bolt or replacement upper, the bolt catch stops working. Magazines that hold the bolt open after the last round are a good stopgap but it doesn't offer the same functionality as a standard AR and most ranges won't let you leave an empty magazine in your rifle in order to keep the bolt open and show that it's clear. This is where the Catch22 comes in. The Catch22 is a direct replacement for your standard bolt catch and will work with most common .22lr conversions. The bolt catch is compatible with Spike's Tactical, CMMG, and Tactical Solutions dedicated upper receivers and conversion bolts, as well as similar Ceiner kit conversion bolts.   

The S&W 15-22 magazine will work great with the Catch22 to provide true last-round-hold-open functionality. The only issue with the 15-22 magazines is that they are shorter (front and back length) than a standard AR magazine. To fix this, the AR Catch22 clip-on magazine shim can clip right onto your lower for a quick and easy way to shim the magazine and solve this issue. The clip is easy to install and remove and it allows you to use your standard 15-22 magazines without any modification. One adapter is needed per lower.  

The S&W 15-22 magazine will work great with the Catch22 to provide true last-round-hold-open functionality. The only issue with the 15-22 magazines is that they are shorter (front and back length) than a standard AR magazine. To fix this, AR Catch22 magazine adapters can stick right onto your 15-22 magazines for a quick and easy way to shim the magazine and solve this issue.  One adapter is needed per magazine. 

Magazines like the S&W 15-22 have a strong enough spring to solidly engage the bolt catch after the last round is fired. Some magazines like the KRISS Defiance DMK22 need a bit of help to consistently engage the bolt catch.   This spring is a direct replacement for the stock bolt catch spring and will allow you to use the DMK22 magazines with the Catch22. There aren't any adverse effects from switching to the lighter spring.