On the MarkIII guns, the full length has always had the ugly slab side holder. The HC version was round for years, but was changed a couple of years ago. Both my full length MarkIII's have the old round HC holder, since it's a direct swap. You might be able to find some old stock of the round part, but it may be difficult. All the old MarkI and MarkII guns had the round holder, but it doesn't fit the new guns and isn't available. Forgot to say, I'm sure there was no fault so it must be a money savings for AA.