Compare Semroc Plywood Block or Bulkhead for Heavy Tube 4.0"(2 ring set) SEM-PB-4.0 Semroc Plywood Block or Bulkhead for Heavy Tube 4.0"(2 ring set) SEM-PB-4.0 For Semroc CPL-10… Now: $16.99 Was: $19.99 Add to Cart