Works with triangular cap, great upgrade - VISM M-LOK Handguard, for AR-15/M4

Conflicting answers on this, but I found an instragram post from VISM stating this rail is designed for the triangular cap. So I took a shot and went with it and so glad I did. It was an upgrade to a PSA midlength upper that came with the triangular cap. As others mentioned, I also found sharpie black marks on some portions of the rail, as to hide imperfections. Not sure why, as there were other blemishes and nicks on the front end. Didn't matter to me, as I view my ARs as fighting rifles, which get dinged way worse. The rail pieces are non-standard mlok, but do fit in the m-lok slots. Otherwise, great cost effective upgrade.