The gravel we're recommending for this area of your garden is
10mm Pea Gravel (brown not pink - please check with supplier)
Decorative and cost effective
Gravel is a cost effective material for pathways and seating areas, adding character, charm and some people also feel an increased level of security. We specify the same sub base as a patio (100mm compacted finish of MOT Type 1) and just a 40mm deep layer of gravel to prevent that ‘walking through snow’ feeling that can often be associated with gravel thats been laid too deeply (or directly onto soil).
Not recommended directly adjoining a lawn where it may get kicked onto the lawn and ‘thrown’ by a lawnmower – we’d recommend using a paving, stone or timber edging to prevent gravel migrating onto other surfaces.
If cats are a problem, we’d recommend a 14-20mm angular gravel rather than a 10mm.
Specification:
Excavate the areas shown to 140mm depth and remove associated waste. Supply, lay and compact MOT type 1 limestone to a compacted depth of 100mm. Finish to be 40mm below final level in preparation for gravel.
Supply and spread 10mm Pea Gravel to a consistent depth of 40mm and rake level.