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.750 diameter, For RRA LAR-8 heavy barrel. NOT FOR INSTALLATION WITH M-LOK HANDGUARDS.
.875 diameter, For fluted RRA LAR-8 heavy barrels in .308, .243, and 6.5. Compatible with M-LOK HANDGUARDS.
.937 diameter, For RRA LAR-8 varmint/bull barrel. NOT FOR INSTALLATION WITH M-LOK HANDGUARDS.