The HRD (Hand Retention Device) from JMac Customs is Compact, lightweight, & reversible
The quarter-turn T-slot nuts have different torque specifications depending on the handguard material: 4.0 N⋅m (35 lb⋅in) for attaching metal accessories to metal handguards. 1.7 N⋅m (15 lb⋅in) for attaching polymer or metal accessories to polymer handguards.