For holding plastic, glass, styrofoam, etc.

PART #      THREAD        DIA.        HT.              
R4-5-MSC        M4          19mm    35mm 
R4-10-MSC      M4          19mm    40mm
R20-5-SC      1/4-20         .75"      1.38"
R20-10-SC    1/4-20         .75"      1.58"