1 with tongue and groove 2 dry and straight 3 cheap price ... ,3.8*3.8cm etc. dry, straight and light. easy to assemble with little knotsChinese fir wood stretcher bar, size;1.5 ... ,3.8*3.8cm etc,dry, straight,cheap and strong. easy to assemblepine wood stretcher bar, size 1.5*2.5cm ... .8*3.8cm etc,good quality, strong, straight,good colour, easy to assemble wood stretcher bars with tongue and groove