Abstract: A non-slip and anti-burring gas cylinder spanner for tightening and loosening hose coupling nuts used with gas cylinder valves includes a body with a handle extending opposite a head. A nut engaging portion within the head defines an internal aperture having at least five nut engaging sides dimensioned and configured to engage corresponding sides of a hexagonal nut so the sides of the nut engaging element have increased contact points with the sides of the nut, preventing slippage and burring. A backing plate attached to the head is positioned over a part of the nut engaging element so the backing plate indicates correct spanner/nut positioning and prevents slippage of the spanner relative to the nut when tightening or loosening. The nut engaging element and the backing plate combination prevents rotational and side slippage of the spanner relative to the nut and burring of the nut when tightening and loosening.